Error in vcpkg_download_distfile.cmake renaming temp dir (may be docker-related)

Package: xerces-c:x64-windows
Vcpkg version: 0.0.113-nohash

I don't think the issue is really in xerces-c. It happens most frequently when running multiple "vcpkg install" commands in separate docker RUN steps. However, I have also reproduced by hand trying to install xerces-c.

The system is a VMware virtual machine running Windows Server 2016 (MSDN licence), running VS2015 in a docker image. The docker image is created from [here](https://gitlab.com/codelibre/containers/vs2015-windows) and [here](https://gitlab.com/codelibre/containers/tools-windows). Could the filesystem behaviour under docker be part of the problem?

See e.g. [this build log](https://gitlab.com/codelibre/containers/ome-files-build-windows-vs2015/-/jobs/95461742)

```
Building package xerces-c[core]:x64-windows...
CMake Error at scripts/cmake/vcpkg_download_distfile.cmake:74 (file):
file RENAME failed to rename

C:/vcpkg/downloads/temp

to

C:/vcpkg/downloads/temp0

because: No such file or directory

Call Stack (most recent call first):
scripts/cmake/vcpkg_from_github.cmake:108 (vcpkg_download_distfile)
ports/xerces-c/portfile.cmake:19 (vcpkg_from_github)
scripts/ports.cmake:71 (include)
```

I can't see any problem with the logic in the script; it's failing, but that shouldn't be possible. It should only try to rename the directory if it exists, so this condition should not occur.