Deprecate ONE_SHOT_MAKEFILE

mm is now doing the same thing as mma. Now print a deprecation message
for other tools that may be setting ONE_SHOT_MAKEFILE directly (or users
that are still using a very old envsetup.sh).

Test: mm  # does not print
Test: ONE_SHOT_MAKEFILE=bionic m
Change-Id: I98221657024d824a61c0d721d5c7dd1a2ea2fb1e