dev-lang/{rust, rust-host}: BDEPEND on llvm

This is an attempt to make sure the llvm-project inside Rust builds
with the regular ebuild clang, not the bootstrap clang. This is
necessary to make sure the profdata generated for PGO is supported.

BUG=b:237786394,b:242227982

Change-Id: I595ffd529a8b0bee3d7be6478d8c6f6bed3ac6e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/chromiumos-overlay/+/3830249
Tested-by: Michael Benfield <mbenfield@google.com>
Reviewed-by: Christopher Di Bella <cjdb@google.com>
2 files changed