Invalid VCSVersion.inc generation when the remote is another folder on Windows

It's probably a very niche situation, but it's a bug anyway.

If you have the remote set as another folder:
```
git remote -v
origin  X:\repos\llvm-project\ (fetch)
origin  X:\repos\llvm-project\ (push)
````

Then `build/tools/clang/lib/Basic/VCSVersion.inc` might look something like:
```
...
#define LLVM_REPOSITORY "X:\repos\llvm-project\"
...
```
Which is invalid because of the escapes.