`-Ctarget-feature`s get ignored after `crt-static`

[Gelbpunkt]

Since #140920, any target-features set after crt-static are silently completely ignored by rustc.

I noticed this while trying to run the testsuite with crt-static = false in bootstrap.toml, which then resulted in a bunch of ABI and target-feature tests failing in very odd ways. Related Zulip thread.

This will be fixed by #144143.