Reland "Consistently prepend arch-specific headers"

This reverts commit cacb972dcda2ee9e537af467f04f1e8cb1b7cb4f.

Relanding along with one more fix in prebuilts/ndk

Change-Id: I65cbc3c5d72bb47bd00e123c63911c9baa1e5f03
Test: m checkbuild
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