Disable rules for making target build of libbcc

These rules add stuff to $(ALL_MODULES.libbcc.REQUIRED), which affects
the host build as well (this seems to be a bug/misfeature in the build
system).  Since we're only building the host variant here, and don't
want to bother building prerequisites for the target variants, just
eliminate the rules for the target build.
If the host arch does not match one of the android arches, just make ARM the default target
Fix endianness bug in writeAndroidBitcodeWrapper()