Support compiler prefix x86_64-linux-musl

[justsmth]

Motivation

• See: aws/aws-lc-rs#736

Context

I found that in some (most?) environments, the musl compiler to use for targeting x86_64-unknown-linux-gnu is prefixed with x86_64-linux-musl. For example, on Ubuntu (AMD64) the musl-dev package contains /usr/bin/x86_64-linux-musl-gcc but it does not contain /usr/bin/musl-gcc, which is provided by the musl-tools package. (The musl-tools package depend on musl-dev.)

When musl-tools is installed, /usr/bin/musl-gcc is simply a symlink to the former:

❯ file /usr/bin/musl-gcc
/usr/bin/musl-gcc: symbolic link to x86_64-linux-musl-gcc

Change

This adds another compiler prefix (x86_64-linux-musl) to check for when building for this target.

[madsmtm]

Thanks, this seems to make sense, although if musl-gcc is a fallback to x86_64-linux-musl-gcc in all situations, I'd prefer to not do fallback, and only attempt to use x86_64-linux-musl-gcc (just like we do for the similar aarch64-linux-musl-gcc).

[justsmth]

Thanks, this seems to make sense, although if musl-gcc is a fallback to x86_64-linux-musl-gcc in all situations, I'd prefer to not do fallback, and only attempt to use x86_64-linux-musl-gcc (just like we do for the similar aarch64-linux-musl-gcc).

I kept the inclusion of the musl prefix (and listed first) as I'm not certain whether Ubuntu's packages are necessarily representative of how other Linux distributions provide the MUSL binaries. Since previously the only prefix checked was musl, keeping it helps avoid breaking consumers that (for whatever reason) only have a musl-gcc compiler in their path.

[madsmtm]

My issue with that is that it seems wrong still? E.g. if cross-compiling from aarch64-unknown-linux-musl to x86_64-unknown-linux-musl, you'll likely also have musl-gcc in your path, but it'll point to the wrong thing.

[justsmth]

My issue with that is that it seems wrong still? E.g. if cross-compiling from aarch64-unknown-linux-musl to x86_64-unknown-linux-musl, you'll likely also have musl-gcc in your path, but it'll point to the wrong thing.

Yeah, that's fair. In the latest commit, it only uses the x86_64-linux-musl prefix.

[madsmtm]

Excellent, thanks!

Will be released next Friday.