Undefine _FORTIFY_SOURCE for release builds

LTO and _FORTIFY_SOURCE interact very, very badly on ubuntu. Ubuntu
implicitly defines it in the compiler (by way of a compiler patch) or
we wouldn't notice since we don't pay attention to CXXFLAGS.
Standardize link flags
Merge pull request #124 from cmaloney/pacify_ubuntu_gcc

Pacify ubuntu gcc
Fix path to stig compiler in run_tests.py
Merge pull request #126 from cmaloney/fix_run_tests_path

Fix path to stig compiler in run_tests.py