openmoko-minimal-image: use rootfs_update_timestamp instead

* use the built in function of image class
applied changes from 1cee605475c1c58340e6f3e491ae0b9d8a3c49ac
             through e73e91ee63bd4489923caaf93614c803d9be457d

diff --git a/packages/images/openmoko-minimal-image.bb b/packages/images/openmoko-minimal-image.bb
index bb25df1..678400f 100644 (file)
--- a/packages/images/openmoko-minimal-image.bb
+++ b/packages/images/openmoko-minimal-image.bb
@@ -18,4 +18,4 @@ DEPENDS = "\
 
 inherit image
 
-ROOTFS_POSTPROCESS_COMMAND += 'date "+%m%d%H%M%Y" >${IMAGE_ROOTFS}/etc/timestamp'
+ROOTFS_POSTPROCESS_COMMAND += "rootfs_update_timestamp;"