util/lint/lint: Fix shellcheck errors in getopt support for darwin

Posix shell doesn't support '=='

Change-Id: Icbdc4204f4c07d806e721fa39f96694c4df00e8d
Signed-off-by: Martin Roth <gaumless@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/81285
Reviewed-by: Patrick Georgi <patrick@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/lint/lint

@@ -30,7 +30,7 @@ junit_write () {
 }
 
 # Look if we have getopt. If not, build it.
-if [ $(uname) == Darwin ]; then
+if [ "$(uname)" = "Darwin" ]; then
   GETOPT="getopt hIJ"
 else
   GETOPT="getopt -l help,junit,invert -o hIJ"