Revert "Android.mk: fix overridden cflags @existz"

This reverts commit fa7f01d404b1737ee6ae1c85422a18edd88911e1.
Revert "Android.mk: Workaround GCC trunk PR57393"

This reverts commit 0ddef5f80d294acd306191bd870c1aa5819d8fa0.