rom.sh: Don't build coreboot utils if dry=":"

This fixes a build error when doing ./mk release, after
a regression caused by the last few commits.

Signed-off-by: Leah Rowe <leah@libreboot.org>

include/rom.sh

@@ -81,7 +81,7 @@ coreboot_pad_one_byte()
 
 mkcorebootbin()
 {
-	fx_ check_coreboot_util printf "cbfstool\nifdtool\n"
+	$dry fx_ check_coreboot_util printf "cbfstool\nifdtool\n"
 
 	for y in "$target_dir/config"/*; do
 		defconfig="$y"