perf: ensure HGRCPATH is exported on Windows After dropping the garbage collector hack, `hg perfstartup` started yelling about not being able to import the evolve extension, which I have in my user config. Launching `env` shows that an empty HGRCPATH isn't exported to the environment. Since `env` doesn't quote, I have no idea if the variable is trimmed, but Mercurial doesn't complain when processing it.

test-status: glob fixes for Windows