rustbuild should warn on quotes in PATH

[retep998]

I have had two people already get an ambiguous failed to execute command: The system cannot find the file specified. error when running rustbuild, and both times it was determined to be as a result of quotes in their PATH. Rustbuild should detect this ahead of time and warn/error.

cc @alexcrichton

[arielb1]

Merely having quotes somewhere random in the path is not the problem. The problem is that cmake (or some other program) is found in a path that contains quotes.

e.g. if you do

> set PATH="C:\Program Files\CMake\bin";%PATH%
> cmake --version
this works
> python src\bootstrap\bootstrap.py
but this doesn't

[retep998]

" is an invalid character for filename paths, and serves absolutely no purpose in PATH, so I'd argue rustbuild should always warn/error about quotes in PATH since it is an obvious mistake, and even if it doesn't break the build, it would be nice to inform the user.

[alexcrichton]

Just to clarify what needs to happen here, should the logic basically be to call as_str on env::var("PATH") and check to see if it contains "? If that happens then abort saying that command execution may not work?

I'm curious why cmd.exe would work when rustbuild doesn't, should we perhaps spawn processes differently?

[retep998]

@alexcrichton It is just cmd which is special and handles PATH in a special way (probably for backwards compatibility reasons). Even powershell can't work with paths that have quotes in them. So we're not doing anything wrong.

Anyway yeah, just scan PATH for any " and emit an error if there is one.

[alexcrichton]

Ok! In that case I'll tag this as E-easy

[c3st7n]

I'd like to take this one..

[retep998]

@c3st7n Sorry to disappoint you but someone already opened a PR to fix this a couple days ago. #34996