libandroidfw: Make sure to set the 'app as lib' flag

When an app is loaded as a shared library (eg. monochrome),
make sure to set the bit that it loaded as such, so that
conversions from package ID 7f -> shared library ID are done.

Bug: 72511998
Test: make libandroidfw_tests
Test: out/host/<host_os>/nativetest64/libandroidfw_tests/libandroidfw_tests
Change-Id: Icd11b7a5adff351165ca16d5853fb5a0002c34b1