Remove asset dir glob files

I'm rewriting how globs work in soong to make them compatible with
hash-based ninja implementations. As part of this, I'm removing this
unnecessary usage of globs to make them simpler.

In this case, since we're already globbing the directory at analysis
time and causing soong to rerun, we can ensure the aapt2 action also
reruns by putting a hash of the glob results onto the command line.

Bug: 364749114
Test: m framework-res, touch frameworks/base/core/res/assets/test1.txt, m framework-res rebuilt framework-res.apk, rm frameworks/base/core/res/assets/test1.txt, m framework-res rebuilt framework-res.apk again
Change-Id: I4f666367a9a0fd0dfa42dc51ef3a788a02b41747