Merge from GCC upstream into GCC/Rust

[Thomas Schwinge <thomas@codesourcery.com>]

Hi "Testers"!

I'm preparing a merge from GCC upstream into GCC/Rust.  This is normally
pretty unexciting ;-) -- the exception being, as once mentioned in
<https://github.com/Rust-GCC/gccrs/issues/247#issuecomment-812720604>:

| Aside from the GCC/Rust-specific files (not existing in GCC upstream),
| we also carry a lot of changes in 'gcc/config/' (GCC back ends
| implementations), originating in <https://github.com/SimplyTheOther>
| "@SimplyTheOther"'s work on Rust Target Hooks.  For a few of these
| files/changes we run into merge conflicts (which I did sort out), but
| also this work may need updates corresponding to GCC upstream changes.
| As that work is (per the Git commit logs etc.) still very much work in
| progress, and I assume hasn't been tested with all the respective many
| GCC back ends, I'm not going to spend much effort on that, and just
| make sure that x86_64-pc-linux-gnu continues to work.

As for checking that the configurations that you're testing are still
fine, would you like to do (and/or fix) that before or after me pushing
the merge?


Grüße
 Thomas
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