Fix mach to let paths in spaces

[wafflespeanut]

#9442 is not only an issue for Windows, but for all platforms, i.e., mach exits if there's space in its path. Though #9601 adds a helpful suggestion, we should fix it.

[larsbergstrom]

This should also include CI tests for all of our build platforms (Windows, OSX, and Linux), as it's super-easy to either break it or pick up a new dependency that doesn't support spaces in paths.

[tigercosmos]

I tried this for a while. Space will just cause lots of problems. LOL

[tigercosmos]

Even virtualenv has not solved space issue yet. pypa/virtualenv#53

[tigercosmos]

@wafflespeanut How do you think if we work at a tmp folder then mv to servo and delete tmp in "space path case". This can solve this issue in another way.

[pradyunsg]

virtualenv has fixed this. Is this still a problem for servo?

[jdm]

Ooh, sounds like we should update the version of virtualenv we rely on.

[pshaughn]

I observed something that I think falls under this: mach will quickly print an informative error and exit if it's being run in a directory that itself contains spaces, but if it's being run in a spaceless one while $HOME does contain spaces, it will instead try to run and then print a much less informative error about not being able to access the Cargo configuration. An explicit check for spaces in the user's home directory, around the same place it's already checking for them in the working directory, could make things friendlier.