Library archives compile the win32 libc shim TU for windows triples

- compileLibArchive now mirrors compileC's win32 arm: scr_win.c joins the archive's object list for x86_64-windows-gnu, providing stpcpy and arc4random_buf (scr_number.c, scr_lib.c, and scr_bytes_io.c call them; mingw's CRT has neither)
- Without it every win32 library archive carried undefined refs no embedder link could resolve — caught by the cross-target library lane's probe links on its first run
- The system-DLL imports (advapi32's CSPRNG/GetUserNameA, iphlpapi's GetAdaptersAddresses, ws2_32's inet_ntop/htonl) stay the embedder's link line: an archive carries no -l flags
- Host archives cannot change by a byte: the TU is gated on targetPlatform(driver) === "win32" and is an empty TU elsewhere anyway