hwasan: Read shadow address from ifunc if we don't need a frame record.

This saves a cbz+cold call in the interceptor ABI, as well as a realign
in both ABIs, trading off a dcache entry against some branch predictor
entries and some code size.

Unfortunately the functionality is hidden behind a flag because ifunc is
known to be broken on static binaries on Android.

Differential Revision: https://reviews.llvm.org/D57084

llvm-svn: 351989