CI Check for code cleanness

[sbryngelson]

Can add a CI check for the introduction of code uncleanness by diffing an MFC build on a PR and on master, both with an appended -Wall flag to the GNU compile options in CMakeLists.txt, piping the output as ./mfc.sh build > out.txt 2>&1, and printing and counting the warnings via grep '\-W' out.txt. Then deleting common lines.