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>

config.mak.uname

@@ -365,7 +365,7 @@ ifeq ($(uname_S),Windows)
 		compat/win32/dirent.o
 	COMPAT_CFLAGS = -D__USE_MINGW_ACCESS -DNOGDI -DHAVE_STRING_H -DHAVE_ALLOCA_H -Icompat -Icompat/regex -Icompat/win32 -DSTRIP_EXTENSION=\".exe\"
 	BASIC_LDFLAGS = -IGNORE:4217 -IGNORE:4049 -NOLOGO -SUBSYSTEM:CONSOLE -NODEFAULTLIB:MSVCRT.lib
-	EXTLIBS = user32.lib advapi32.lib shell32.lib wininet.lib ws2_32.lib
+	EXTLIBS = user32.lib advapi32.lib shell32.lib wininet.lib ws2_32.lib invalidcontinue.obj
 	PTHREAD_LIBS =
 	lib =
 ifndef DEBUG