[swift-dev] Build script and archival steps for the toolchain

[Philippe Hausler]

I find myself building toolchains very often; with the scripts I am using I am immediately installing to the current Xcode toolchain locations and a considerable amount of time is being spent in creating a tarball of the toolchain (which I don’t really need, but I need all of the steps up-to that point).

I was thinking of adding a new flag to skip the tar command; I did not readily see a way to skip this step but do all of the rest. Is this something useful for others?