Create APEX variation only when needed

Create an APEX variation of a module only when it is either directly
included in an APEX or the dependency to the module demands that the
module should be included. For example, a non-static dependency to a
java library no longer creates an APEX variant of the library.

Bug: 146907857
Test: m (apex_test amended)
Test: cat out/soong/build.ninja | grep "Module:" | wc -l
reduced from 47132 to 45881

Change-Id: Icd79fb4b60668d852b9f018343b934b5e42a8eda

apex/apex.go

@@ -105,7 +105,8 @@ func apexDepsMutator(mctx android.BottomUpMutatorContext) {
 				android.UpdateApexDependency(apexBundleName, depName, directDep)
 			}
 
-			if am, ok := child.(android.ApexModule); ok && am.CanHaveApexVariants() {
+			if am, ok := child.(android.ApexModule); ok && am.CanHaveApexVariants() &&
+				(directDep || am.DepIsInSameApex(mctx, child)) {
 				am.BuildForApex(apexBundleName)
 				return true
 			} else {