Support asan/hwasan versions of prebuilts.

In apex_set and cc_prebuilt_library_*, provide a way to specify an
alternative source to use when build with sanitizers.

Test: prebuilt_test, apex_test
Change-Id: I1ab8091bf696d94da3547cf5248853df489bdee6
diff --git a/cc/library.go b/cc/library.go
index 35828aa..f5b2b65 100644
--- a/cc/library.go
+++ b/cc/library.go
@@ -121,7 +121,10 @@
 }
 
 type StaticOrSharedProperties struct {
-	Srcs   []string `android:"path,arch_variant"`
+	Srcs []string `android:"path,arch_variant"`
+
+	Sanitized Sanitized `android:"arch_variant"`
+
 	Cflags []string `android:"arch_variant"`
 
 	Enabled            *bool    `android:"arch_variant"`