Makefile: add CFLAGS and LDFLAGS to Makefile to support memkind
Makefile: add CFLAGS and LDFLAGS to Makefile to support memkind

The high-bandwidth memory allocators are part of memkind, which we must link
explicitly, so add the link flags to do this. We also add the "USE_HBM" option
to the Makefile to enable or disable these flags.

rcthomas/resist,rcthomas/resist