fix car:app:app configuration caching
fix car:app:app configuration caching

Bug: 180423646

Test: enable configuration caching, run busytown/androidx.sh, and that there is no longer an error in :car:app:app:generateProtocolApi saying:

  Extension of type 'LibraryExtension' does not exist.

Change-Id: I4682e522baabb01c53619aa1b6144f0da826657a

androidx/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx