Merge pull request #843 from rust-lang/fix/debuginfo-lang-filename #1956

Job	Run time
build (--test-libcore)	42s
build (--test-successful-rustc --nb-parts 2 --current-part 0)	52s
build (--std-tests)	44s
build (--mini-tests)	43s
build (--test-successful-rustc --nb-parts 2 --current-part 1)	52s
success_gcc12	3s
	3m 56s

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