Install prefix

[cholcombe973]

This new version of rustup no longer supports an install prefix. I need that for my automated builds in snappy.

[brson]

rustup installs to two locations, represented by CARGO_HOME and RUSTUP_HOME, and that cannot be represented with a single prefix. To change where rustup installs, set both these variables while running rustup-init. Note though that these two environment variables must remain set during execution of the Rust toolchain.

I believe this is yet-undocumented, and there may be better interfaces.

cc #994

[cholcombe973]

@brson thanks! I'll give this a shot soon. I think that'll solve my issue

[kornelski]

BTW, snapcraft in Debian remains broken by this change. Since that's a built-in plugin, I don't have a way to fix it.

Given that Debian moves at glacial pace, this is going to remain defunct for a long time. It'll be best if Rustup re-added --prefix, --disable-sudo and --save, at least as no-ops.