Don't set /SUBSYSTEM:WINDOWS in librarian options
Don't set /SUBSYSTEM:WINDOWS in librarian options

Based on the description of it (see https://docs.microsoft.com/en-gb/cpp/build/reference/managing-a-library?view=vs-2019 and https://docs.microsoft.com/en-gb/cpp/build/reference/subsystem-specify-subsystem?view=vs-2019), it seems a bit weird to set it on a library.

Additionally, removing it works around a problem when using Clang and llvm-lib.
msquared2/pfc,msquared2/pfc