libtool: backported os/2 support patches:

OS/2 versioning support is commented out as an SDL customization..
Orig patchset: https://github.com/komh/libtool-os2/tree/2.4.2-os2

acinclude/libtool.m4

@@ -2560,9 +2560,34 @@ os2*)
   libname_spec='$name'
   shrext_cmds=".dll"
   need_lib_prefix=no
-  library_names_spec='$libname${shared_ext} $libname.a'
+  # OS/2 limits length of a DLL basename up to 8 characters.
+  # So there is need to use a short name instead of a original
+  # name longer than 8 characters. And replace '.' with '_'.
+# SDL customization: removed versioning support.
+# version_type=windows
+# need_version=no
+# soname_spec='`test -n "$os2dllname" && libname="$os2dllname";
+#   v=$($ECHO ${release}${versuffix} | tr -d .-);
+#   n=$($ECHO $libname | cut -b -$((8 - ${#v})) | tr . _);
+#   $ECHO ${n}${v}`${shared_ext}'
+  soname_spec='`test -n "$os2dllname" && libname="$os2dllname"; $ECHO $libname | cut -b -8 | tr . _`${shared_ext}'
+  library_names_spec='${libname}_dll.$libext'
   dynamic_linker='OS/2 ld.exe'
-  shlibpath_var=LIBPATH
+  shlibpath_var=BEGINLIBPATH
+  sys_lib_search_path_spec="/lib /usr/lib /usr/local/lib"
+  sys_lib_dlsearch_path_spec="$sys_lib_search_path_spec"
+  postinstall_cmds='base_file=`basename \$file`~
+    dlpath=`$SHELL 2>&1 -c '\''. $dir/'\''\$base_file'\''i; $ECHO \$dlname'\''`~
+    dldir=$destdir/`dirname \$dlpath`~
+    test -d \$dldir || mkdir -p \$dldir~
+    $install_prog $dir/$dlname \$dldir/$dlname~
+    chmod a+x \$dldir/$dlname~
+    if test -n '\''$stripme'\'' && test -n '\''$striplib'\''; then
+      eval '\''$striplib \$dldir/$dlname'\'' || exit \$?;
+    fi'
+  postuninstall_cmds='dldll=`$SHELL 2>&1 -c '\''. $file; $ECHO \$dlname'\''`~
+    dlpath=$dir/\$dldll~
+    $RM \$dlpath'
   ;;
 
 osf3* | osf4* | osf5*)
@@ -3158,6 +3183,9 @@ sysv4 | sysv4.3*)
 tpf*)
   lt_cv_deplibs_check_method=pass_all
   ;;
+os2*)
+  lt_cv_deplibs_check_method=pass_all
+  ;;
 esac
 ])
 file_magic_cmd=$lt_cv_file_magic_cmd
@@ -3588,6 +3616,11 @@ m4_if([$1], [CXX], [
       # (--disable-auto-import) libraries
       m4_if([$1], [GCJ], [],
 	[_LT_TAGVAR(lt_prog_compiler_pic, $1)='-DDLL_EXPORT'])
+      case $host_os in
+      os2*)
+	_LT_TAGVAR(lt_prog_compiler_static, $1)='${wl}-static'
+	;;
+      esac
       ;;
     darwin* | rhapsody*)
       # PIC is the default on this platform
@@ -3895,6 +3928,11 @@ m4_if([$1], [CXX], [
       # (--disable-auto-import) libraries
       m4_if([$1], [GCJ], [],
 	[_LT_TAGVAR(lt_prog_compiler_pic, $1)='-DDLL_EXPORT'])
+      case $host_os in
+      os2*)
+	_LT_TAGVAR(lt_prog_compiler_static, $1)='${wl}-static'
+	;;
+      esac
       ;;
 
     darwin* | rhapsody*)
@@ -3963,6 +4001,11 @@ m4_if([$1], [CXX], [
       # built for inclusion in a dll (and should export symbols for example).
       m4_if([$1], [GCJ], [],
 	[_LT_TAGVAR(lt_prog_compiler_pic, $1)='-DDLL_EXPORT'])
+      case $host_os in
+      os2*)
+	_LT_TAGVAR(lt_prog_compiler_static, $1)='${wl}-static'
+	;;
+      esac
       ;;
 
     hpux9* | hpux10* | hpux11*)
@@ -4353,6 +4396,34 @@ _LT_EOF
       fi
       ;;
 
+    os2*)
+      _LT_TAGVAR(hardcode_libdir_flag_spec, $1)='-L$libdir'
+      _LT_TAGVAR(hardcode_minus_L, $1)=yes
+      _LT_TAGVAR(allow_undefined_flag, $1)=unsupported
+      shrext_cmds=".dll"
+      _LT_TAGVAR(archive_cmds, $1)='$ECHO "LIBRARY ${soname%$shared_ext} INITINSTANCE TERMINSTANCE" > $output_objdir/$libname.def~
+	$ECHO "DESCRIPTION \"$libname\"" >> $output_objdir/$libname.def~
+	$ECHO "DATA MULTIPLE NONSHARED">> $output_objdir/$libname.def~
+	$ECHO EXPORTS >> $output_objdir/$libname.def~
+	emxexp $libobjs | $SED /"_DLL_InitTerm"/d >> $output_objdir/$libname.def~
+	$CC -Zdll -Zcrtdll -o $output_objdir/$soname $libobjs $deplibs $compiler_flags $output_objdir/$libname.def~
+	emximp -o $lib $output_objdir/$libname.def'
+      _LT_TAGVAR(archive_expsym_cmds, $1)='$ECHO "LIBRARY ${soname%$shared_ext} INITINSTANCE TERMINSTANCE" > $output_objdir/$libname.def~
+	$ECHO "DESCRIPTION \"$libname\"" >> $output_objdir/$libname.def~
+	$ECHO "DATA MULTIPLE NONSHARED">> $output_objdir/$libname.def~
+	$ECHO EXPORTS >> $output_objdir/$libname.def~
+	prefix_cmds="$SED"~
+	if test "x`$SED 1q $export_symbols`" = xEXPORTS; then
+	  prefix_cmds="$prefix_cmds -e 1d";
+	fi~
+	prefix_cmds="$prefix_cmds -e \"s/^\(.*\)$/_\1/g\""~
+	cat $export_symbols | $prefix_cmds >> $output_objdir/$libname.def~
+	$CC -Zdll -Zcrtdll -o $output_objdir/$soname $libobjs $deplibs $compiler_flags $output_objdir/$libname.def~
+	emximp -o $lib $output_objdir/$libname.def'
+      _LT_TAGVAR(old_archive_From_new_cmds, $1)='emximp -o $output_objdir/${libname}_dll.a $output_objdir/$libname.def'
+      _LT_TAGVAR(enable_shared_with_static_runtimes, $1)=yes
+      ;;
+
     interix[[3-9]]*)
       _LT_TAGVAR(hardcode_direct, $1)=no
       _LT_TAGVAR(hardcode_shlibpath_var, $1)=no
@@ -4913,8 +4984,28 @@ _LT_EOF
       _LT_TAGVAR(hardcode_libdir_flag_spec, $1)='-L$libdir'
       _LT_TAGVAR(hardcode_minus_L, $1)=yes
       _LT_TAGVAR(allow_undefined_flag, $1)=unsupported
-      _LT_TAGVAR(archive_cmds, $1)='$ECHO "LIBRARY $libname INITINSTANCE" > $output_objdir/$libname.def~$ECHO "DESCRIPTION \"$libname\"" >> $output_objdir/$libname.def~$ECHO DATA >> $output_objdir/$libname.def~$ECHO " SINGLE NONSHARED" >> $output_objdir/$libname.def~$ECHO EXPORTS >> $output_objdir/$libname.def~emxexp $libobjs >> $output_objdir/$libname.def~$CC -Zdll -Zcrtdll -o $lib $libobjs $deplibs $compiler_flags $output_objdir/$libname.def'
-      _LT_TAGVAR(old_archive_from_new_cmds, $1)='emximp -o $output_objdir/$libname.a $output_objdir/$libname.def'
+      shrext_cmds=".dll"
+      _LT_TAGVAR(archive_cmds, $1)='$ECHO "LIBRARY ${soname%$shared_ext} INITINSTANCE TERMINSTANCE" > $output_objdir/$libname.def~
+	$ECHO "DESCRIPTION \"$libname\"" >> $output_objdir/$libname.def~
+	$ECHO "DATA MULTIPLE NONSHARED">> $output_objdir/$libname.def~
+	$ECHO EXPORTS >> $output_objdir/$libname.def~
+	emxexp $libobjs | $SED /"_DLL_InitTerm"/d >> $output_objdir/$libname.def~
+	$CC -Zdll -Zcrtdll -o $output_objdir/$soname $libobjs $deplibs $compiler_flags $output_objdir/$libname.def~
+	emximp -o $lib $output_objdir/$libname.def'
+      _LT_TAGVAR(archive_expsym_cmds, $1)='$ECHO "LIBRARY ${soname%$shared_ext} INITINSTANCE TERMINSTANCE" > $output_objdir/$libname.def~
+	$ECHO "DESCRIPTION \"$libname\"" >> $output_objdir/$libname.def~
+	$ECHO "DATA MULTIPLE NONSHARED">> $output_objdir/$libname.def~
+	$ECHO EXPORTS >> $output_objdir/$libname.def~
+	prefix_cmds="$SED"~
+	if test "x`$SED 1q $export_symbols`" = xEXPORTS; then
+	  prefix_cmds="$prefix_cmds -e 1d";
+	fi~
+	prefix_cmds="$prefix_cmds -e \"s/^\(.*\)$/_\1/g\""~
+	cat $export_symbols | $prefix_cmds >> $output_objdir/$libname.def~
+	$CC -Zdll -Zcrtdll -o $output_objdir/$soname $libobjs $deplibs $compiler_flags $output_objdir/$libname.def~
+	emximp -o $lib $output_objdir/$libname.def'
+      _LT_TAGVAR(old_archive_From_new_cmds, $1)='emximp -o $output_objdir/${libname}_dll.a $output_objdir/$libname.def'
+      _LT_TAGVAR(enable_shared_with_static_runtimes, $1)=yes
       ;;
 
     osf3*)
@@ -5667,6 +5758,34 @@ if test "$_lt_caught_CXX_error" != yes; then
         _LT_DARWIN_LINKER_FEATURES($1)
 	;;
 
+      os2*)
+	_LT_TAGVAR(hardcode_libdir_flag_spec, $1)='-L$libdir'
+	_LT_TAGVAR(hardcode_minus_L, $1)=yes
+	_LT_TAGVAR(allow_undefined_flag, $1)=unsupported
+	shrext_cmds=".dll"
+	_LT_TAGVAR(archive_cmds, $1)='$ECHO "LIBRARY ${soname%$shared_ext} INITINSTANCE TERMINSTANCE" > $output_objdir/$libname.def~
+	  $ECHO "DESCRIPTION \"$libname\"" >> $output_objdir/$libname.def~
+	  $ECHO "DATA MULTIPLE NONSHARED">> $output_objdir/$libname.def~
+	  $ECHO EXPORTS >> $output_objdir/$libname.def~
+	  emxexp $libobjs | $SED /"_DLL_InitTerm"/d >> $output_objdir/$libname.def~
+	  $CC -Zdll -Zcrtdll -o $output_objdir/$soname $libobjs $deplibs $compiler_flags $output_objdir/$libname.def~
+	  emximp -o $lib $output_objdir/$libname.def'
+	_LT_TAGVAR(archive_expsym_cmds, $1)='$ECHO "LIBRARY ${soname%$shared_ext} INITINSTANCE TERMINSTANCE" > $output_objdir/$libname.def~
+	  $ECHO "DESCRIPTION \"$libname\"" >> $output_objdir/$libname.def~
+	  $ECHO "DATA MULTIPLE NONSHARED">> $output_objdir/$libname.def~
+	  $ECHO EXPORTS >> $output_objdir/$libname.def~
+	  prefix_cmds="$SED"~
+	  if test "x`$SED 1q $export_symbols`" = xEXPORTS; then
+	    prefix_cmds="$prefix_cmds -e 1d";
+	  fi~
+	  prefix_cmds="$prefix_cmds -e \"s/^\(.*\)$/_\1/g\""~
+	  cat $export_symbols | $prefix_cmds >> $output_objdir/$libname.def~
+	  $CC -Zdll -Zcrtdll -o $output_objdir/$soname $libobjs $deplibs $compiler_flags $output_objdir/$libname.def~
+	  emximp -o $lib $output_objdir/$libname.def'
+	_LT_TAGVAR(old_archive_From_new_cmds, $1)='emximp -o $output_objdir/${libname}_dll.a $output_objdir/$libname.def'
+	_LT_TAGVAR(enable_shared_with_static_runtimes, $1)=yes
+	;;
+
       dgux*)
         case $cc_basename in
           ec++*)

ltmain.sh

@@ -805,7 +805,7 @@ func_enable_tag ()
 
 
   case $host in
-    *cygwin* | *mingw* | *pw32* | *cegcc*)
+    *cygwin* | *mingw* | *pw32* | *cegcc* | *os2*)
       # don't eliminate duplications in $postdeps and $predeps
       opt_duplicate_compiler_generated_deps=:
       ;;
@@ -1573,6 +1573,7 @@ The following components of LINK-COMMAND are treated specially:
   -no-undefined     declare that a library does not refer to external symbols
   -o OUTPUT-FILE    create OUTPUT-FILE from the specified objects
   -objectlist FILE  Use a list of object files found in FILE to specify objects
+  -os2dllname NAME  specify short DLL name on OS/2 (no effect on other OSes)
   -precious-files-regex REGEX
                     don't remove output files matching REGEX
   -release RELEASE  specify package release information
@@ -2054,6 +2055,13 @@ func_mode_install ()
 	      ;;
 	    esac
 	    ;;
+	  os2*)
+	    case $realname in
+	    *_dll.a)
+	      tstripme=
+	      ;;
+	    esac
+	    ;;
 	  esac
 	  if test -n "$tstripme" && test -n "$striplib"; then
 	    func_show_eval "$striplib $destdir/$realname" 'exit $?'
@@ -4085,6 +4093,7 @@ func_mode_link ()
     module=no
     no_install=no
     objs=
+    os2dllname=
     non_pic_objects=
     precious_files_regex=
     prefer_static_libs=no
@@ -4331,6 +4340,11 @@ func_mode_link ()
 	  prev=
 	  continue
 	  ;;
+	os2dllname)
+	  os2dllname="$arg"
+	  prev=
+	  continue
+	  ;;
 	precious_regex)
 	  precious_files_regex="$arg"
 	  prev=
@@ -4622,6 +4636,11 @@ func_mode_link ()
 	continue
 	;;
 
+      -os2dllname)
+	prev=os2dllname
+	continue
+	;;
+
       -o) prev=output ;;
 
       -precious-files-regex)
@@ -4775,6 +4794,17 @@ func_mode_link ()
         continue
         ;;
 
+      # OS/2 uses -Zxxx to specify OS/2-specific options
+      -Z*)
+	compiler_flags="$compiler_flags $arg"
+	func_append compile_command " $arg"
+	func_append finalize_command " $arg"
+	case $arg in
+	-Zlinker | -Zstack) prev=xcompiler;;
+	esac
+	continue
+	;;
+
       # Some other compiler flag.
       -* | +*)
         func_quote_for_eval "$arg"
@@ -5557,7 +5587,7 @@ func_mode_link ()
 	if test -n "$library_names" &&
 	   { test "$use_static_libs" = no || test -z "$old_library"; }; then
 	  case $host in
-	  *cygwin* | *mingw* | *cegcc*)
+	  *cygwin* | *mingw* | *cegcc* | *os2*)
 	      # No point in relinking DLLs because paths are not encoded
 	      notinst_deplibs="$notinst_deplibs $lib"
 	      need_relink=no
@@ -5627,7 +5657,7 @@ func_mode_link ()
 	    elif test -n "$soname_spec"; then
 	      # bleh windows
 	      case $host in
-	      *cygwin* | mingw* | *cegcc*)
+	      *cygwin* | mingw* | *cegcc*)  # | *os2* # SDL customization: removed OS/2 versioning support.
 	        func_arith $current - $age
 		major=$func_arith_result
 		versuffix="-$major"