The .gz, .bz2 or .lzma are middle files for making gz.u-boot,
bz2.u-boot, or lzma.u-boot. It should be removed once the final
image is generated. Otherwise, even RM_OLD_IMAGE = 1, it can't
be removed, moreover more and more middle files are genrated via
'bitbake *-image'
Signed-off-by: Yue Tao <Yue.Tao@windriver.com> Signed-off-by: Roy Li <rongqing.li@windriver.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
