Allow Strip in Debuggable

Allow Strip to be set in Debuggable builds.

Bug: 171273461
Test: manual confirmation
Change-Id: Ief259891e8e3fd19b31377e92fbbad28daa405ac

android/variable.go

@@ -90,6 +90,11 @@ type variableProperties struct {
 			Required        []string
 			Host_required   []string
 			Target_required []string
+			Strip           struct {
+				All                          *bool
+				Keep_symbols                 *bool
+				Keep_symbols_and_debug_frame *bool
+			}
 		}
 
 		// eng is true for -eng builds, and can be used to turn on additionaly heavyweight debugging