Rollup merge of #126008 - Zalathar:fulldeps-19371, r=jieyouxu

Port `tests/run-make-fulldeps/issue-19371` to ui-fulldeps

This test can run as an ordinary `tests/ui-fulldeps` test, with the help of some additional header variable substitutions to supply a sysroot and linker.

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Unlike #125973, this test appears to be testing something vaguely useful and breakable, which is why I didn't just delete it.

Author: matthiaskrgr