mingw: make core.fsyncObjectFiles default explicit

Now that we have a `batch` mode, let's be explicit.

This is a follow-up to ce4786f (mingw: change core.fsyncObjectFiles
= 1 by default, 2017-09-04) and will most likely have to be squashed
into it before upstreaming that patch (after the `batch` fsync mode was
upstreamed).

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

compat/mingw.c

@@ -3603,7 +3603,7 @@ int wmain(int argc, const wchar_t **wargv)
 
 	maybe_redirect_std_handles();
 	adjust_symlink_flags();
-	fsync_object_files = 1;
+	fsync_object_files = FSYNC_OBJECT_FILES_ON;
 
 	/* determine size of argv and environ conversion buffer */
 	maxlen = wcslen(wargv[0]);