Fix 8.3~ expansion

[andyneff]

1. On github actions, the default temp directory ends up having a component longer than 8 characters, so the short 8.3 version of the path got picked up somewhere.
2. When this path is handed to the conda installer it incorrectly claims this is an invalid path because all ~'s are invalid. This invalidation is clearly invalid.
3. cygpath can be used to expand to the long format
4. But cygpath will fail to expand if the entire path doesn't already exist (even if the part that needs to be expanded does exist)

This quick fix attempts to handle that so conda install quits erroring