Migrate `cross-lang-lto-upstream-rlibs`, `long-linker-command-lines` and `long-linker-command-lines-cmd-exe` `run-make` tests to rmake
Part of #121876 and the associated [Google Summer of Code project](https://blog.rust-lang.org/2024/05/01/gsoc-2024-selected-projects.html).
The `long-linker` tests are certainly doing something... interesting - they summon `rustc` calls with obscene quantities of arguments and check that this is appropriately handled. I removed the `RUSTC_ORIGINAL` magic - it's equivalent to `RUSTC` in `tools.mk`, so what is the purpose? Making it so the massive pile of flags doesn't modify rustc itself and start leaking into other tests? Tell me what you think.
Please try:
try-job: x86_64-msvc
try-job: i686-msvc
try-job: x86_64-mingw
try-job: i686-mingw
try-job: aarch64-apple
try-job: test-various
try-job: x86_64-gnu-debug
try-job: x86_64-gnu-llvm-17
The run-make test suite contains tests which are the most flexible out of all
the rust-lang/rust test suites. run-make
tests can basically contain arbitrary code, and are supported by the
run_make_support library.
Infrastructure
There are two kinds of run-make tests:
The new rmake.rs version: this allows run-make tests to be written in Rust
(with rmake.rs as the main test file).
The legacy Makefile version: this is what run-make tests were written with
before support for rmake.rs was introduced.
The implementation for collecting and building the rmake.rs recipes (or
Makefiles) are in
src/tools/compiletest/src/runtest.rs,
in run_rmake_v2_test and run_rmake_legacy_test.
Rust-based run-make tests: rmake.rs
The setup for the rmake.rs version is a 3-stage process:
First, we build the run_make_support library in bootstrap as a tool lib.
Then, we compile the rmake.rs "recipe" linking the support library and its
dependencies in, and provide a bunch of env vars. We setup a directory
structure within build/<target>/test/run-make/
<test-name>/
rmake.exe # recipe binary
rmake_out/ # sources from test sources copied over
and copy non-rmake.rs input support files over to rmake_out/. The
support library is made available as an extern prelude.
Finally, we run the recipe binary and set rmake_out/ as the working
directory.
Formatting
Note that files under tests/ are not formatted by ./x fmt,
use rustfmt tests/path/to/file.rs to format a specific file if desired.
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