A couple of fixes for using Makefile.standalone on Mac.

A couple of fixes for using Makefile.standalone on Mac.

(*) PNaCl toolchain_build builds 64-bit libraries for LLVM on Mac.
    That won't link with subzero code if subzero is built with -m32,
    so add an option to override the -m32.
(*) include locale header
(*) Mark xMacroIntegrityCheck unused to avoid clang compiler warning.
(*) virtual dtor, for inheritable class
(*) Mark compare function const

BUG=none
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/428733003