rustc_driver: Frob the global PATH less

Environment variables are global state so this can lead to surprising results if
the driver is called in a multithreaded environment (e.g. doctests). There
shouldn't be any memory corruption that's possible, but a lot of the bots have
been failing because they can't find `cc` or `gcc` in the path during doctests,
and I highly suspect that it is due to the compiler modifying `PATH` in a
multithreaded fashion.

This commit moves the logic for appending to `PATH` to only affect the child
process instead of also affecting the parent, at least for the linking stage.
When loading dynamic libraries the compiler still modifies `PATH` on Windows,
but this may be more difficult to fix than spawning off a new process.

0 files changed, 0 insertions, 0 deletions