On Windows, static vs DLL linking affects details in quite a few
cases, so it's good to have coverage for both cases.
Testing with static linking also increases coverage for a number of
cases and individual checks that have had to be waived for the DLL
case, and allows testing libc++experimental, increasing the number
of test cases actually executed by 180 (176 new tests from
libc++experimental and 4 ones that are XFAIL windows-dll).