Use the installation script from a release instead of the main branch

[jessebraham]

This is being left as a draft until I can confirm that it is a viable path forward.

Rather than pulling the installation script from the main branch of rust-build, we will now use the script provided in the release corresponding to the specified compiler version.

In order for this to work a couple things must hold true:

• We must continue to format all release tags as v{major}.{minor}.{patch}.{build}
• The MinGW Binary 12 and LLVM Project 14.0 Minified version releases MUST stay marked as pre-release and must NOT be converted to proper releases

@georgik @SergioGasquez please let me know what you think of this.

Closes #7.

[SergioGasquez]

LGTM! I think the two conditions required for this to work are entirely accepted. Even more, in the future, we should be able to remove the prereleases of MinGW and LLVM