Fix finding src directory for aidl

aidlFlags was always looking for a src directory at the top level
instead of in the module's source directory.

Test: m checkbuild
Change-Id: Ie31baa21c8632c2bd9a6ebc42e6291417b1f31cd
diff --git a/java/java.go b/java/java.go
index fbd7bdd..8941b4d 100644
--- a/java/java.go
+++ b/java/java.go
@@ -374,7 +374,7 @@
 	flags = append(flags, android.JoinWithPrefix(j.exportAidlIncludeDirs.Strings(), "-I"))
 	flags = append(flags, android.JoinWithPrefix(localAidlIncludes.Strings(), "-I"))
 	flags = append(flags, "-I"+android.PathForModuleSrc(ctx).String())
-	if src := android.ExistentPathForSource(ctx, "", "src"); src.Valid() {
+	if src := android.ExistentPathForSource(ctx, "", ctx.ModuleDir(), "src"); src.Valid() {
 		flags = append(flags, "-I"+src.String())
 	}