Auto merge of #47035 - acfoltzer:dep-info-tweak, r=alexcrichton

Auto merge of #47035 - acfoltzer:dep-info-tweak, r=alexcrichton

Remove dep-info files as targets in themselves

If you ask `rustc` to `--emit dep-info`, the resulting dependency file contains a rule for producing the dependency file itself. This differs from the output of `gcc -MD` or `clang -MD`, which only includes dependency rules for the object files produced.

Tools like Ninja often consume and delete dependency files as soon as they’re produced for performance reasons, particularly on Windows. In the case of `rustc` output, though, the recently-deleted dependency file is cached by Ninja as a target, and therefore triggers a rebuild every time.

This very small patch removes the dep-info file from the list of output filenames, so it matches the behavior of gcc and clang.