Migrate `run-make/issue64319` to `rmake` and rename
Part of #121876 and the associated [Google Summer of Code project](https://blog.rust-lang.org/2024/05/01/gsoc-2024-selected-projects.html).
~~I noticed that the Makefile was not listed in `allowed-run-makefiles` in Tidy. Does this mean the test was being ignored?~~ EDIT: No, it was there, just not in its expected alphabetical order.
EDIT2: Perhaps it could be interesting to clean this test visually by looping over the `rustc` calls, like in #125227.
Migrate `run-make/no-cdylib-as-rdylib` 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 test will fail if the cdylib is picked, because it doesn't export any rust symbols"
Is that true? Is there a way to verify?
I suggest maybe extending the test with: (after cleaning the directory)
```rust
rustc()
.input("bar.rs")
.crate_type("cdylib")
.run();
rustc()
.input("foo.rs")
.prefer_dynamic()
.run();
fail();
```
to make sure we're actually testing something here.
Use new utility functions/methods in run-make tests
Little cleanup using new functions/methods I added into the `run-make-support` library.
r? `@jieyouxu`
Migrate `run-make/issue-14500` to new `rmake.rs` format
Part of #121876 and the associated [Google Summer of Code project](https://blog.rust-lang.org/2024/05/01/gsoc-2024-selected-projects.html).
Note: I find suspicious that `libbar.a` is hardcoded and is not using the `STATICLIB` call to adapt to Windows platforms. Is this intentional? If not, this will need to be changed.
Rewrite 3 very similar `run-make` alloc tests to rmake
Part of #121876#121918 attempted to port these 3 tests 2 months ago. However, since then, the structure of `run-make-support` has changed a bit and new helper functions were added. Since there has been no activity on the PR, they are good low-hanging fruit to knock down, using the new functions of the current library.
There is also the removal of a useless import on a very similar test.
Migrate rustdoc scrape examples ordering
Part of https://github.com/rust-lang/rust/issues/121876.
This one adds a lot of utility methods/functions. To prevent having too much changes at once, I didn't make the existing rmake tests use these yet but I'll send a follow-up so they all use it.
r? `@jieyouxu`
Display walltime benchmarks with subnanosecond precision
With modern CPUs running at more than one cycle per nanosecond the current precision is insufficient to resolve differences worth several cycles per iteration.
Granted, walltime benchmarks often are noisy but occasionally, especially when no allocations are involved, the difference really is just a few cycles.
example results when benchmarking 1-4 serialized ADD instructions and an empty bench body
```
running 4 tests
test add ... bench: 0.24 ns/iter (+/- 0.00)
test add2 ... bench: 0.48 ns/iter (+/- 0.01)
test add3 ... bench: 0.72 ns/iter (+/- 0.01)
test add4 ... bench: 0.96 ns/iter (+/- 0.01)
test empty ... bench: 0.24 ns/iter (+/- 0.00)
```
