MSVC: link in invalidcontinue.obj for better POSIX compatibility

By default, Windows abort()'s instead of setting errno=EINVAL when invalid arguments are passed to standard functions. For example, when PAGER quits and git detects it with errno=EPIPE on write(), check_pipe() in write_or_die.c tries raise(SIGPIPE) but since there is no SIGPIPE on Windows, it is treated as invalid argument, causing abort() and crash report window. Linking in invalidcontinue.obj (provided along with MS compiler) allows raise(SIGPIPE) to return with errno=EINVAL. Signed-off-by: Marat Radchenko <marat@slonopotamus.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>