Split Java libraries per apex

Just like native libs, a java library that is included in an APEX is
mutated for the APEX. This allows us to infer the context (e.g.
sdk_version, etc.) for building a java library in an APEX.

Bug: 138182343
Test: apex_test added
Change-Id: I9292ea097b98e74a8a794f164bd2bed3921d6337

java/hiddenapi_singleton.go

@@ -152,6 +152,14 @@ func stubFlagsRule(ctx android.SingletonContext) {
 		// Collect dex jar paths for modules that had hiddenapi encode called on them.
 		if h, ok := module.(hiddenAPIIntf); ok {
 			if jar := h.bootDexJar(); jar != nil {
+				// For a java lib included in an APEX, only take the one built for
+				// the platform variant, and skip the variants for APEXes.
+				// Otherwise, the hiddenapi tool will complain about duplicated classes
+				if a, ok := module.(android.ApexModule); ok {
+					if android.InAnyApex(module.Name()) && !a.IsForPlatform() {
+						return
+					}
+				}
 				bootDexJars = append(bootDexJars, jar)
 			}
 		}