genimage.bbclass: derive better default for GENIMAGE_ROOTFS_IMAGE_FSTYPE

Instead of hard-coding tar.bz2, use the first element in IMAGE_FSTYPES
matching a tar format.

Signed-off-by: Enrico Jörns <ejo@pengutronix.de>

classes-recipe/genimage.bbclass

@@ -103,8 +103,15 @@ GENIMAGE_IMAGE_LINK_NAME = "${IMAGE_BASENAME}-${MACHINE}"
 GENIMAGE_IMAGE_FULLNAME ?= "${GENIMAGE_IMAGE_NAME}.${GENIMAGE_IMAGE_SUFFIX}"
 GENIMAGE_IMAGE_LINK_FULLNAME ?= "${GENIMAGE_IMAGE_LINK_NAME}.${GENIMAGE_IMAGE_SUFFIX}"
 
+def get_default_fstype(d):
+    fstypes = d.getVar('IMAGE_FSTYPES' or '').split()
+    for x in fstypes:
+        if "tar" in x:
+            return x
+    return "tar.bz2"
+
 GENIMAGE_ROOTFS_IMAGE ?= ""
-GENIMAGE_ROOTFS_IMAGE_FSTYPE ?= "tar.bz2"
+GENIMAGE_ROOTFS_IMAGE_FSTYPE ?= "${@get_default_fstype(d)}"
 GENIMAGE_ROOTFS_IMAGE_SUFFIX ?= "${IMAGE_NAME_SUFFIX}"
 
 GENIMAGE_VARIABLES[IMAGE] = "${GENIMAGE_IMAGE_FULLNAME}"