When testing different linkers, it's sometimes useful to run the tests
with `SWIFT_DRIVER_TEST_OPTIONS=" -use-ld=<linker>"`. If we do this,
it will break a handful of tests because they expect the compiler driver
to choose an appropriate linker automatically.
To avoid having these fail, detect when someone has done this, and
set a new feature, `linker_overridden`, then mark the tests in question
with `UNSUPPORTED: linker_overridden`.
rdar://123504095
The librarian on Windows is a part of the linker. Enabling `-use-ld=`
for driver for static linking on Windows enables the user to override
the linker. This is particularly important for cross-linking Windows
from Linux where link.exe is not present as it is a part of the MSVC
toolset.
It was previously capturing the output but not checking it. Actually
validate the output. Fix the windows invocation check. Ensure that we
disable the logo for the librarian on Windows.
