tools/firmware-utils: use UTC for image timestamps

By using localtime() to determine the timestamp that goes into factory
images, the resulting image depends on the timezone of the build system.
Use gmtime() instead, which results in more reproducible images.

Signed-off-by: Sander Vanheule <sander@svanheule.net>

tools/firmware-utils/Makefile

@@ -7,7 +7,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME := firmware-utils
-PKG_RELEASE := 1
+PKG_RELEASE := 2
 
 include $(INCLUDE_DIR)/host-build.mk
 include $(INCLUDE_DIR)/kernel.mk

tools/firmware-utils/src/addpattern.c

@@ -296,7 +296,7 @@ int main(int argc, char **argv)
 		return EXIT_FAILURE;
 	}
 
-	ptm = localtime(&t);
+	ptm = gmtime(&t);
 
 	if (3 != sscanf(version, "v%d.%d.%d", &v0, &v1, &v2)) {
 		fprintf(stderr, "bad version string \"%s\"\n", version);

tools/firmware-utils/src/tplink-safeloader.c

@@ -2079,7 +2079,7 @@ static struct image_partition_entry make_soft_version(uint32_t rev) {
 	else if (time(&t) == (time_t)(-1))
 		error(1, errno, "time");
 
-	struct tm *tm = localtime(&t);
+	struct tm *tm = gmtime(&t);
 
 	s->magic = htonl(0x0000000c);
 	s->zero = 0;