Revert "Consistently prepend arch-specific headers"

This reverts commit e945a4d212edd9c15805b9787e9a56f214244431.

Reason for revert: broke full-eng checkbuild

Change-Id: I0036fed96aa727b63c16982151fd661923e77e59
diff --git a/cc/library.go b/cc/library.go
index 196d575..93bd56c 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,variant_prepend"`
+	Export_include_dirs []string `android:"arch_variant"`
 
 	// 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,variant_prepend"`
+	Export_system_include_dirs []string `android:"arch_variant"`
 
 	Target struct {
 		Vendor, Product struct {