Auto merge of #10322 - eholk:reserved-windows-name, r=ehuss

Test if reserved filenames are allowed in Windows

Recent versions of Windows have removed the limitation on filenames like `aux` or `con`. This change allows the `package::reserved_windows_name` to still pass by first trying to create a file with a reserved name to see if Windows supports it. If so, it skips the rest of the test. Otherwise, we keep the same behavior as before.