Currently mirrors are stored in the rust-lang-ci2 S3 bucket along with
CI toolchains. This is problematic for multiple reasons:
- CI IAM credentials are allowed to both edit and delete those files.
A malicious user gaining access to those credentials would be able to
change our mirrored dependencies, possibly backdooring the compiler.
- Contents of the rust-lang-ci2 bucket are disposable except for the
mirrors' content. When we implement backups for S3 buckets we'd have
to replicate just that part of the bucket, complicating the backup
logic and increasing the chance of mistakes. A standalone bucket will
be way easier to backup.
This commit switches our CI to use the new rust-lang-ci-mirrors bucket.
The main goal here is to use FreeBSD's normal libc++, instead of
statically linking the libstdc++ packaged with GCC, because that
libstdc++ has bugs that cause rustc to deadlock inside LLVM.
But the easiest way to use libc++ is to switch the build from GCC to
Clang, and the Clang package in the Ubuntu image already knows how to
cross-compile (given a sysroot and preferably cross-binutils), so the
toolchain script now uses that instead of building a custom compiler.
This also de-duplicates the `build-toolchain.sh` script.
Pietro Albini
Alex Crichton
Mark Rousskov
Jed Davis