kbuild: Call gzip with -n

The timestamps recorded in the .gz files add no value.
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/Makefile.lib

@@ -197,7 +197,7 @@ cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@
 # ---------------------------------------------------------------------------
 
 quiet_cmd_gzip = GZIP    $@
-cmd_gzip = (cat $(filter-out FORCE,$^) | gzip -f -9 > $@) || \
+cmd_gzip = (cat $(filter-out FORCE,$^) | gzip -n -f -9 > $@) || \
 	(rm -f $@ ; false)
 
 # DTC

scripts/gen_initramfs_list.sh

@@ -226,7 +226,7 @@ cpio_list=
 output="/dev/stdout"
 output_file=""
 is_cpio_compressed=
-compr="gzip -9 -f"
+compr="gzip -n -9 -f"
 
 arg="$1"
 case "$arg" in
@@ -240,7 +240,7 @@ case "$arg" in
 		output_file="$1"
 		cpio_list="$(mktemp ${TMPDIR:-/tmp}/cpiolist.XXXXXX)"
 		output=${cpio_list}
-		echo "$output_file" | grep -q "\.gz$" && compr="gzip -9 -f"
+		echo "$output_file" | grep -q "\.gz$" && compr="gzip -n -9 -f"
 		echo "$output_file" | grep -q "\.bz2$" && compr="bzip2 -9 -f"
 		echo "$output_file" | grep -q "\.lzma$" && compr="lzma -9 -f"
 		echo "$output_file" | grep -q "\.xz$" && \