Migrate `incr-add-rust-src-component` to rmake
This PR partially supersedes #128562, and ports the Makefile-based `tests/run-make/incr-add-rust-src-component` to use rmake.rs infra.
Part of #121876.
This run-make test is a regression test for https://github.com/rust-lang/rust/issues/70924. It (tries to) checks that if we add the `rust-src` component in between two incremental compiles, that the compiler doesn't ICE on the second invocation.
- Original issue:https://github.com/rust-lang/rust/issues/70924
- Fix PR: https://github.com/rust-lang/rust/pull/72767
- PR adding this regression test: https://github.com/rust-lang/rust/pull/72952
However, the Makefile version of this used `$SYSROOT/lib/rustlib/src/rust/src/libstd/lib.rs`, but that actually got moved around and reorganized over the years. As of Dec 2024, the `rust-src` component is more like (specific for our purposes):
```
$SYSROOT/lib/rustlib/src/rust/
library/std/src/lib.rs
src/
```
However, this run-make test is ancient and it exercises incr-comp system logic. I'm not sure if this test would actually catch the original regression.
This PR was co-authored with `@Oneirical.`
r? incremental
try-job: i686-msvc
try-job: x86_64-mingw-1
try-job: x86_64-msvc
try-job: aarch64-apple
c016cd8670