finer-grained so we can build 2024.1.29 too.
* fix(mvfst) missing linux header closes #5038 closes #5119 * maybe? dirty. * ...why was the test script rebuilding it? * sigh * just painful * kill me now * wip * hm * wip * punt. with a comment. not happy.
* fix(mvfst) closes #3896 * 🎵i hate everything...🎶
* new file: projects/facebook.com/mvfst/CMakeLists.txt new file: projects/facebook.com/mvfst/package.yml * maybe with llvm * CMAKE_ARGS * -latomic * wip