tools/mkimage: create .itb file with read-access for group,other not just owner.

This patch will fix the source of 403 errors on these files
from downloads.openwrt.org.

Signed-off-by: Ted Hess <thess@kitschensync.net>

tools/mkimage/patches/020-fix-file-creation-perms.patch

@@ -0,0 +1,11 @@
+--- a/tools/fit_image.c
++++ b/tools/fit_image.c
+@@ -642,7 +642,7 @@ static int copyfile(const char *src, con
+ 		goto out;
+ 	}
+ 
+-	fd_dst = open(dst, O_WRONLY | O_CREAT, 0700);
++	fd_dst = open(dst, O_WRONLY | O_CREAT, 0744);
+ 	if (fd_dst < 0) {
+ 		printf("Can't open file %s (%s)\n", dst, strerror(errno));
+ 		goto out;