rustc: Support output filenames for each emit type

Currently the compiler supports the ability to emit multiple output types as
part of one compilation (e.g. asm, LLVM IR, bytecode, link, dep-info, etc). It
does not, however, support the ability to customize the output filename for each
of these output types. The `-o` flag is ignored if multiple emit types are
specified (and the compiler emits a warning about this).

Normally this doesn't matter too much, but in the case of `dep-info` it can lead
to a number of problems (e.g. see #28716). By allowing customization of the
output filename for each emit type we're able to solve the problems in that
issue.

This commit adds support for the `--emit` option to the compiler to look like:

    rustc foo.rs --emit dep-info=.deps/foo.d,link

This indicates that the `dep-info` output type will be placed at `.deps/foo.d`
and the `link` output type will otherwise be determined via the `--out-dir` and
`-o` flags.

Closes #28716

0 files changed, 0 insertions, 0 deletions