From the tidy source, it looks like this is checking for files in git which have the executable permission bit set. I would imagine this is directly caused by running on NTFS, which doesn't have such an executable bit.
The test is disabled on windows, but apparently not on Linux running NTFS! I'd recommend filing a bug report on the rust-lang/rust repo.
In the meantime, cloning on a non-NTFS filesystem should work around the error.