Test(lib/win/proc): Skip `raw_attributes` doctest under Win7
The current doctest for `ProcThreadAttributeListBuilder::raw_attribute` uses `CreatePseudoConsole`, which is only available on Windows 10 October 2018 Update and above. On older versions of Windows, the test fails due to trying to link against a function that is not present in the kernel32 DLL. This therefore ensures the test is still built, but not run under the Win7 target.
@rustbot label T-libs A-process A-doctests O-windows-7
Jonathan Brouwer
893abbca37