Add more Cygwin support

[500-internal-server-error]

Makes more things compile on Cygwin. Basically a continuation of #9535. This requires a pending PR to nix, and after that some packages need to be updated to allow it to compile out of the box on Cygwin.

[oech3]

You don't need to care about uname -s since MSYS2 overrides OS.

[500-internal-server-error]

You don't need to care about uname -s since MSYS2 overrides OS.

I don't think so, it still carries the Windows default "Windows_NT", at least on my machine. I need some way to tell apart native Windows and Cygwin.

[500-internal-server-error]

Hmm, not sure why style is failing, I've already formatted the pieces I touched. Will format again anyway.

[oech3]

MSYS package builds fine without make OS=.... Do you use non-MSYS cygwin?

[oech3]

Oh sorry. You are right. Cygwin is not Windows_NT...

[500-internal-server-error]

MSYS package builds fine without make OS=.... Do you use non-MSYS cygwin?

It does build fine, but that's because it skips UNIX_PROGS. Since $(OS) == Windows_NT, it assumes not Unix, even though Cygwin should be treated as Unix.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

[500-internal-server-error]

Hmm network failures...

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)

[sylvestre]

any update on this? thanks

[500-internal-server-error]

Still waiting on nix, which is waiting on libc. Unless you don't mind using [patch.crates-io] and needing to unpatch it when it properly releases on crates.io.

[oech3]

Merging this is still useful to reduce num of patches at packaging even if we need newer nix and libc.

[oech3]

Also note that updating libc at here is delaying due to FreeBSD issue: #8722

[500-internal-server-error]

Merging this is still useful to reduce num of patches at packaging even if we need newer nix and libc.

If not being buildable out of the box is fine then technically this PR could be merged as is.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)

[sylvestre]

ok, sounds good!