kbuild: Fix size_append issue for bzip2/lzma kernel

The Makefile.lib will call "echo -ne" to append uncompressed kernel size to
bzip2/lzma kernel image.
The "echo" here depends on the shell that /bin/sh pointing to.
On Ubuntu system, the /bin/sh is pointing to dash, which does not support
"echo -e" at all. Use /bin/echo instead of shell echo should always be safe.

Signed-off-by: Alek Du <alek.du@intel.com>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

scripts/Makefile.lib

@@ -208,7 +208,7 @@ cmd_gzip = (cat $(filter-out FORCE,$^) | gzip -f -9 > $@) || \
 
 # Bzip2 and LZMA do not include size in file... so we have to fake that;
 # append the size as a 32-bit littleendian number as gzip does.
-size_append = echo -ne $(shell						\
+size_append = /bin/echo -ne $(shell					\
 dec_size=0;								\
 for F in $1; do								\
 	fsize=$$(stat -c "%s" $$F);					\