The current way adds a lot of ordering assumptions, and doesn't fit too
well with parallel batch fuzzing either. Add a "upload-build" boolean action
input that can be added to "build_fuzzers" to upload latest builds
instead.
Builds are now uploaded by commit hash, rather than a fixed "latest" name.
ClusterFuzzLite's download_latest_build will check the last 3 commits and download the
first available build by git hash.