build: Don't default to underscore=yes for cross-build.

* acinclude.m4: Don't set ac_cv_sys_symbol_underscore
for cross build.

--

It made sense in the past when cross compile were basically for a.out
system, but nowadays, it's better not to assume that.

Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>

acinclude.m4

@@ -111,14 +111,10 @@ case "${host}" in
         ac_cv_sys_symbol_underscore=yes
         ;;
     *)
-      if test "$cross_compiling" = yes; then
-        if test "x$ac_cv_sys_symbol_underscore" = x ; then
-           ac_cv_sys_symbol_underscore=yes
-        fi
-      else
+      if test "$cross_compiling" != yes; then
          tmp_do_check="yes"
       fi
-       ;;
+      ;;
 esac
 if test "$tmp_do_check" = "yes"; then
   AC_REQUIRE([AC_LIBTOOL_SYS_GLOBAL_SYMBOL_PIPE])