Optimize PathForBazelOutRelative

This isn't benchmarked or anything, but should give
minor performance improvements.

Test: Verified ninja files didn't change on aosp_arm64-userdebug
Change-Id: I030991f91c326669b7b7e73b8171da4b2a68cbb4
diff --git a/android/mutator.go b/android/mutator.go
index d92b87c..4e55609 100644
--- a/android/mutator.go
+++ b/android/mutator.go
@@ -409,7 +409,7 @@
 
 	return &bottomUpMutatorContext{
 		bp:                ctx,
-		baseModuleContext: a.base().baseModuleContextFactory(ctx),
+		baseModuleContext: moduleContext,
 		finalPhase:        finalPhase,
 	}
 }