Rename DexJar interface method to DexJarBuildPath.

This is a prerequisite change before adding DexJarInstallPath.

Test: lunch aosp_cf_phone-userdebug && m
Change-Id: I033e08b8bb06c0a844a6bbbfcdc48ce33e9c95cf
diff --git a/java/aar.go b/java/aar.go
index c8daf83..7413c80 100644
--- a/java/aar.go
+++ b/java/aar.go
@@ -730,7 +730,7 @@
 	return android.Paths{a.classpathFile}
 }
 
-func (a *AARImport) DexJar() android.Path {
+func (a *AARImport) DexJarBuildPath() android.Path {
 	return nil
 }