Rollup merge of #123316 - Enselic:sigpipe-inherit-variants, r=fmease

Test `#[unix_sigpipe = "inherit"]` with both `SIG_DFL` and `SIG_IGN`

Extend our `#[unix_sigpipe = "inherit"]` test so that it detects if  `SIGPIPE` wrongly ends up being `SIG_DFL` when the parent has `SIG_IGN`. We have no current test for this particular case.

Tracking issue: rust-lang/rust#97889

Author: fmease