Split CommonGlobalIncludes for system includes

Split CommonGlobalSystemIncludes out of CommonGlobalIncludes in
preparation for moving global includes from -isystem to -I.

Bug: 31492149
Change-Id: Ib935ea038cdbf9515dc2ab68d7fff924c370906a

cc/compiler.go

@@ -147,6 +147,7 @@ func (compiler *baseCompiler) compilerFlags(ctx ModuleContext, flags Flags) Flag
 		if !ctx.sdk() || ctx.Host() {
 			flags.GlobalFlags = append(flags.GlobalFlags,
 				"${config.CommonGlobalIncludes}",
+				"${config.CommonGlobalSystemIncludes}",
 				tc.IncludeFlags(),
 				"${config.CommonNativehelperInclude}")
 		}

cc/config/global.go

@@ -90,9 +90,11 @@ func init() {
 	pctx.StaticVariable("CommonClangGlobalCppflags",
 		strings.Join(append(ClangFilterUnknownCflags(commonGlobalCppflags), "${ClangExtraCppflags}"), " "))
 
-	// Everything in this list is a crime against abstraction and dependency tracking.
+	// Everything in these lists is a crime against abstraction and dependency tracking.
 	// Do not add anything to this list.
-	pctx.PrefixedPathsForOptionalSourceVariable("CommonGlobalIncludes", "-isystem ",
+	pctx.PrefixedPathsForOptionalSourceVariable("CommonGlobalIncludes", "-I",
+		[]string{})
+	pctx.PrefixedPathsForOptionalSourceVariable("CommonGlobalSystemIncludes", "-isystem ",
 		[]string{
 			"system/core/include",
 			"system/media/audio/include",

cc/makevars.go

@@ -44,7 +44,7 @@ func makeVarsProvider(ctx android.MakeVarsContext) {
 	ctx.Strict("GLOBAL_CLANG_CPPFLAGS_NO_OVERRIDE", "")
 	ctx.Strict("NDK_PREBUILT_SHARED_LIBRARIES", strings.Join(ndkPrebuiltSharedLibs, " "))
 
-	includeFlags, err := ctx.Eval("${config.CommonGlobalIncludes}")
+	includeFlags, err := ctx.Eval("${config.CommonGlobalIncludes} ${config.CommonGlobalSystemIncludes}")
 	if err != nil {
 		panic(err)
 	}