default to using gzip with mksquashfs if lzma and xz are unavailable

SVN-Revision: 27748

include/image.mk

@@ -42,6 +42,7 @@ ifneq ($(CONFIG_JFFS2_LZMA),y)
   JFFS2OPTS += -x lzma
 endif
 
+SQUASHFSCOMP := gzip
 LZMA_XZ_OPTIONS := -Xpreset 9 -Xe -Xlc 0 -Xlp 2 -Xpb 2
 ifeq ($(CONFIG_SQUASHFS_LZMA),y)
   SQUASHFSCOMP := lzma $(LZMA_XZ_OPTIONS)