[netcore] Avoid touching or using submodules in coreonly mode

Makefile.am

@@ -19,11 +19,17 @@ build_with_msvc =
 build_without_msvc = msvc
 endif
 
+if ENABLE_NETCORE
+update_submodules = 
+else
+update_submodules = update_submodules
+endif
+
 SUBDIRS = $(build_with_msvc) mk po $(libgc_dir) llvm mono $(ikvm_native_dir) support data runtime scripts man samples $(tools_dir) $(build_without_msvc) $(docs_dir) acceptance-tests
 # Keep in sync with SUBDIRS
 DIST_SUBDIRS = $(build_with_msvc) m4 mk po $(libgc_dir) llvm mono ikvm-native support data runtime scripts man samples tools $(build_without_msvc) docs acceptance-tests netcore
 
-all: update_submodules
+all: $(update_submodules)
 
 update_submodules:
 	@cd $(srcdir) && scripts/update_submodules.sh

configure.ac

@@ -6410,7 +6410,9 @@ AC_SUBST(CPPFLAGS)
 AC_SUBST(LDFLAGS)
 
 # Update all submodules recursively to ensure everything is checked out
-(cd $srcdir && scripts/update_submodules.sh)
+if test "x$with_core" != "xonly"; then
+	(cd $srcdir && scripts/update_submodules.sh)
+fi
 
 AC_OUTPUT([
 Makefile

mono/Makefile.am

@@ -12,6 +12,10 @@ if MONO_NATIVE
 native_dirs = native
 endif
 
+if ENABLE_NETCORE
+btls_dirs = 
+endif
+
 if CROSS_COMPILING
 SUBDIRS = $(btls_dirs) eglib arch utils cil $(sgen_dirs) metadata mini dis profiler $(native_dirs)
 else