Let findSupportedAbi and hasRenderscriptBitcode scan only relevant files

for better performance. Without the optimization, these two functions
may check more than 100k file names in the pre-installed APK files,
which can take a few seconds to finish even on a recent device.

Bug: 21957428
Change-Id: I315fd3c6d5aa1076b993752525de449a9933de12