Rollup merge of #123975 - lqd:rust-lld-tests, r=jieyouxu

Port the 2 `rust-lld` run-make tests to `rmake`

In preparation for finalizing most of the `rust-lld` work, this PR ports the following tests to `rmake`:
- `tests/run-make/rust-lld`
- `tests/run-make/rust-lld-custom-target`

As they use `$(CGREP) -e` I added `regex` as an exported dependency to the `run_make_support` library.

Unfortunately, the most recent versions depend on `memchr` 2.6.0 but it's currently pinned at 2.5.0 in the workspace, and therefore had to settle for the older `regex-1.8.0`.

r? `@jieyouxu`

Author: GuillaumeGomez