Hi,

https://github.com/dotnet/sdk/blob/main/src/Common/PathUtilities.cs#L24 uses mkdir on linux and Directory.CreateDirectory on windows.
This leads to a behavior difference where some directory can not be created if TMPDIR is a path which doesn't exist on linux (it fails) and it passes on windows.

I propose to drop the linux specificity and keep using the Directory API + chmod after directory creation if 0700 perms are desired.