Consistently prepend arch-specific headers

Add variant_prepend to Export_include_dirs, Export_system_include_dirs
and Generated_headers to match Local_include_dirs so that
architecture-specific headers are found before common headers.

Test: m checkbuild
Test: TestIncludeDirectoryOrdering
Change-Id: I2bf9d4373fd256e500c1f8d6c84cf593e8fdd170
diff --git a/cc/cc_test.go b/cc/cc_test.go
index 2d0d78b..ef413fe 100644
--- a/cc/cc_test.go
+++ b/cc/cc_test.go
@@ -4345,12 +4345,12 @@
 		"${config.ArmToolchainClangCflags}",
 		"${config.ArmClangArmv7ANeonCflags}",
 		"${config.ArmClangGenericCflags}",
-		"export_include_dirs",
-		"linux_export_include_dirs",
-		"android_export_include_dirs",
-		"arm_export_include_dirs",
-		"lib32_export_include_dirs",
 		"android_arm_export_include_dirs",
+		"lib32_export_include_dirs",
+		"arm_export_include_dirs",
+		"android_export_include_dirs",
+		"linux_export_include_dirs",
+		"export_include_dirs",
 		"android_arm_local_include_dirs",
 		"lib32_local_include_dirs",
 		"arm_local_include_dirs",
diff --git a/cc/compiler.go b/cc/compiler.go
index 78a5a5d..69ead30 100644
--- a/cc/compiler.go
+++ b/cc/compiler.go
@@ -92,7 +92,7 @@
 
 	// list of generated headers to add to the include path. These are the names
 	// of genrule modules.
-	Generated_headers []string `android:"arch_variant"`
+	Generated_headers []string `android:"arch_variant,variant_prepend"`
 
 	// pass -frtti instead of -fno-rtti
 	Rtti *bool
diff --git a/cc/library.go b/cc/library.go
index 93bd56c..196d575 100644
--- a/cc/library.go
+++ b/cc/library.go
@@ -183,11 +183,11 @@
 	// be added to the include path (using -I) for this module and any module that links
 	// against this module.  Directories listed in export_include_dirs do not need to be
 	// listed in local_include_dirs.
-	Export_include_dirs []string `android:"arch_variant"`
+	Export_include_dirs []string `android:"arch_variant,variant_prepend"`
 
 	// list of directories that will be added to the system include path
 	// using -isystem for this module and any module that links against this module.
-	Export_system_include_dirs []string `android:"arch_variant"`
+	Export_system_include_dirs []string `android:"arch_variant,variant_prepend"`
 
 	Target struct {
 		Vendor, Product struct {