Downstream CI for `libc`

[tgross35]

libc is tested a handful of places downstream for targets that aren't Tier 2+, or have less common configurations. This issue is intended to aggregate a list of any such public CI.

Targets	Maintainer	Link	Status Badge

If you are interested in testing a target that can be run in Docker or natively on GitHub Actions (e.g. with a self-hosted runner), see https://github.com/tgross35/libc-downstream-ci for a simple template to get a daily job going.

If you are already running CI downstream anywhere with public results, comment a link and I'll update the table.

[tgross35]

Cc @Gelbpunkt @asomers @semarie @maurer @skrap @neuschaefer @sunshowers @erickt @Nashenas88 @ivmarkov @MabezDev @SergioGasquez because I believe all of you have either expressed interest in running downstream CI, or are already doing so.