This patch fixes two bugs in upstream mcookie detection: 1) If mcookie is not
detected, we still need to set HAS_COOKIE_HANDLER and MK_COOKIE, and 2) the
value for MK_COOKIE must be a string in order to disallow further preprocessor
expansions.

In particular for 2, if we fail to surround the path in quotes, our path
contains the token "linux", which gcc further expands, creating an invalid
path.

--- a/configure.ac	2025-03-08 16:48:34.476791744 +0900
+++ b/configure.ac	2025-03-08 16:48:30.208791623 +0900
@@ -157,8 +157,10 @@
     fi
 fi
 if test "x$MCOOKIE" != x ; then
-	STARTX_COOKIE_FLAGS='-DHAS_COOKIE_MAKER -DMK_COOKIE="$(MCOOKIE)"'
+	STARTX_COOKIE_FLAGS='-DHAS_COOKIE_MAKER -DMK_COOKIE="'"'"'$(MCOOKIE)'"'"'"'
 	AC_MSG_NOTICE([startx will depend on "$MCOOKIE" to generate xauth cookies])
+else
+	STARTX_COOKIE_FLAGS='-DHAS_COOKIE_MAKER -DMK_COOKIE='
 fi
 AC_SUBST(STARTX_COOKIE_FLAGS)