Added two files to .gitignore that are created during a build

MOM6_ALE/build_ale/Makefile and fms_build/Makefile are left behind after a build and show up as untracked files. This makes it appear that MIDAS (as a submodule) has been modified when it has not.

Should fix issue mjharriso/MIDAS#5.
Merge pull request #7 from adcroft-gfdl/master

Added two files to .gitignore that are created during a build