Add arch variant support to android_app_import.

Bug: 128610294
Fixes: 138792623
Test: app_test.go
Change-Id: I47c80ec283ce58a0ce9b7d0af40844bd73e9d3f1
diff --git a/android/arch.go b/android/arch.go
index 44c3f48..907c58b 100644
--- a/android/arch.go
+++ b/android/arch.go
@@ -557,6 +557,10 @@
 	return archType
 }
 
+func ArchTypeList() []ArchType {
+	return append([]ArchType(nil), archTypeList...)
+}
+
 func (a ArchType) String() string {
 	return a.Name
 }