Fix CI url for compiler-rt source

add mips/mips64 compiler-rt fallbacks so that libgcc is not required

https://github.com/rust-lang/rust/pull/72700

 caused the existing
`allow(improper_ctypes)` guard to stop working, we now need
`allow(improper_ctypes_definitions)` instead.

We keep the old one to avoid any issues with older nightlies.

Signed-off-by: Joe Richey <joerichey@google.com>

Co-authored-by: Jethro Beekman <jethro@fortanix.com>

And add an `#[allow]` for now to appease stage0

* Expand wasm32 testing on CI

Run the full `run.sh` test script to get full assertions, including that
nothing in the wasm compiler-builtins is panicking. Unfortunately it's
currently panicking, so this is good to weed out!

* Update libm

Co-authored-by: Tomasz Miąsko <tomasz.miasko@gmail.com>

* Switch to using `llvm_asm!` instead of `asm!`

* Run rustfmt

* Fix how LTO is specified on nightly

Co-authored-by: Tomasz Miąsko <tomasz.miasko@gmail.com>

`AArch64` GCCs exit with an error condition when they encounter any kind of
floating point code if the `nofp` and/or `nosimd` compiler flags have been set.

Therefore, evaluate if those flags are present and set a boolean that causes any
compiler-rt intrinsics that contain floating point source to be excluded for
this target.

This patch prepares https://github.com/rust-lang/rust/pull/68334

This adds compiler-rt fallbacks for mips and mips64 arches.

Solves linking issues like https://github.com/rust-lang/rust/issues/57820

.

Signed-off-by: Yuxiang Zhu <vfreex@gmail.com>

This is necessary because the Mach-O definition must have the
triple underscore, but the UEFI one must not.

* fix compile error on x86_64-unknown-uefi target

* Fix tests on nightly

Don't emit the intrinsics for platforms which don't actually have the
instructions to do atomic loads/stores.

Closes #322

* Allow FFI-unsafe warnings for u128/i128

Handle new warnings on nightly, and we shouldn't need to worry about
these with compiler-builtins since this is tied to a particular compiler.

* Clean up crate attributes

* No need for stability marker
* Rustdoc docs not used for this crate
* Remove old build-system related cruft from rustc itself.

* Run `cargo fmt`

* Emit `_fltused` on `uefi` targets as a short-term workaround

* Remove stray docker container

As of LLVM 9.0, certain calls to memcmp may be converted to bcmp, which I guess
could save a single subtraction on some architectures. [1]

bcmp is just like memcmp except instead of returning the difference between the
two differing bytes, it returns non-zero instead. As such, memcmp is a valid
implementation of bcmp.

If we care about size, bcmp should just call memcmp.
If we care about speed, we can change bcmp to look like this instead:
```rust
pub unsafe extern "C" fn bcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
    let mut i = 0;
    while i < n {
        let a = *s1.offset(i as isize);
        let b = *s2.offset(i as isize);
        if a != b {
            return 1;
        }
        i += 1;
    }
    0
}
```

In this PR I do not address any changes which may or may not be needed for arm
aebi as I lack proper test hardware.

[1]: https://releases.llvm.org/9.0.0/docs/ReleaseNotes.html#noteworthy-optimizations