re PR go/55969 (libgo fails to build on darwin)

	PR go/55969
	* configure.ac: Disable libgo on some systems where it does not
	work.

From-SVN: r195768

configure

@@ -3413,6 +3413,23 @@ case "${target}" in
     ;;
 esac
 
+# Disable libgo for some systems where it is known to not work.
+# For testing, you can easily override this with --enable-libgo.
+if test x$enable_libgo = x; then
+    case "${target}" in
+    *-*-darwin*)
+	# PR 46986
+	noconfigdirs="$noconfigdirs target-libgo"
+	;;
+    *-*-cygwin* | *-*-mingw*)
+	noconfigdirs="$noconfigdirs target-libgo"
+	;;
+    *-*-aix*)
+	noconfigdirs="$noconfigdirs target-libgo"
+	;;
+    esac
+fi
+
 # Default libgloss CPU subdirectory.
 libgloss_dir="$target_cpu"
 

configure.ac

@@ -752,6 +752,23 @@ case "${target}" in
     ;; 
 esac
 
+# Disable libgo for some systems where it is known to not work.
+# For testing, you can easily override this with --enable-libgo.
+if test x$enable_libgo = x; then
+    case "${target}" in
+    *-*-darwin*)
+	# PR 46986
+	noconfigdirs="$noconfigdirs target-libgo"
+	;;
+    *-*-cygwin* | *-*-mingw*)
+	noconfigdirs="$noconfigdirs target-libgo"
+	;;
+    *-*-aix*)
+	noconfigdirs="$noconfigdirs target-libgo"
+	;;
+    esac
+fi
+
 # Default libgloss CPU subdirectory.
 libgloss_dir="$target_cpu"