Add libc_malloc_{debug,hooks}.so to the absence check.

They should only be in the Runtime APEX, c.f. discussion on
http://r.android.com/957159.

Test: build/soong/build_test.bash through Forrest
Bug: 124293228
Change-Id: I33e97a56e67c3f4734d14f38e0f1597b697a2604