This PR adds a hash constant to the Xcode toolchain script, similar to
how upstream `MAC_BINARIES_TAG` on their counterpart of this source.
With this change we check the hash sum when downloading the file to make
sure it matches the expected hash.
Prior to this change, the decision to download/extract a new SDK was
entirely based on the version of the SDK found in the destination path.
This has served us well, however is a weaker scheme for reproducibility
checks. With this change, it is being introduced a scheme, similar to
how this type of check is done in other places, where a sidecar file is
created based on the name of the toolchain to be downloaded, and that
sidecar file has a hashsum in it.
With this new verification scheme we can now detect accidental
overwrites of the toolchain, but we can also leave the door open to use
issue a new toolchain under a subversion in case of some emergency fix
for a toolchain file
Finally, this change also corrects a few things across this source that
are outdated, and do not conform to the python style guide currently
enforced in Chromium, in particular the naming convention that was being
used.
Bug: https://github.com/brave/brave-browser/issues/55812
cdesouza-chromium
7fb251b2fa