Add compile time define that was missing.

There used to be a check for `__has_include(<cxxabi.h>)`, but it
was removed because it is a clang extension. This adds
-DLIBCXX_BUILDING_LIBCXXABI to the mk and bp files to fix this.

Change-Id: Ife2f93ace8c2766c0140fba88bf74a941ed8e57e
2 files changed