Update the gecko-rust-build docker container to upload the constructed toolchain to tooltool when running on taskcluster, so it can be used in normal gecko builds (buildbot as well as tc) Also include a mac build script (which can't run in taskcluster currently) and a python script for launching the build task from a local checkout. This is based on Ted's script for building breakpad's minidump_stackwalk utility. Matches contents of https://github.com/rillian/rust-build commit 407c6854e91541341508e96e6a2781434535b7a5 tag v0.2.0
This is a docker script for building rust toolchains for use in Mozilla's build clusters.