package/guile: drop unrecognized option

Commit d8bee3950aa851620d6a954aebad1f984caa105a forgot to drop
--with-libltdl-prefix

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/guile/guile.mk

@@ -64,7 +64,6 @@ GUILE_CONF_ENV += GUILE_FOR_BUILD=$(HOST_DIR)/bin/guile \
 	CFLAGS="$(TARGET_CFLAGS) $(GUILE_CFLAGS)"
 
 GUILE_CONF_OPTS += \
-	--with-libltdl-prefix=$(STAGING_DIR)/usr/lib \
 	--with-libgmp-prefix=$(STAGING_DIR)/usr/lib \
 	--with-libunistring-prefix=$(STAGING_DIR)/usr/lib