add support for LOCAL_MODULE_STEM_32 and LOCAL_MODULE_STEM_64

Some executables will need to be built for both 32-bit and 64-bit.
For linker/linker64, debuggerd/debuggerd64, and a few more, they
will be installed in the same path (/system/bin), but with different
filenames.  Allow the module to specify LOCAL_MODULE_STEM_32 and
LOCAL_MODULE_STEM_64 to name the two versions.

Change-Id: I573e8678c7332245a064f31246be0a05f0a9e25f