Multiple "warning: could not canonicalize path" at start of any tool invocation

[xaquseg]

Whenever I run any tool (rustup itself, rustc, cargo, seems to impact everything) I get two copies of "warning: could not canonicalize path" for the folder I'm in, and then one for each parent directory, excluding the drive root. This only happens when the current folder is on C:, it doesn't happen for other drives. println!("{:?}", std::fs::canonicalize(r"C:\Users")) doesn't error in a test program, but rustup prints an error for that path.

The tools themselves run properly after the warnings print, and directly running the binaries under .rustup/toolchains/*/bin doesn't print the warnings.

I'm on Windows 7 64 bit.

[Diggsey]

Dupe of #682