docker/coreboot-jenkins-node: Add GNU parallel

Change-Id: I958e65f3c758e7e46d6b628a05009c1b4727d40a
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50087
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/docker/coreboot-jenkins-node/Dockerfile

@@ -25,6 +25,7 @@ USER root
 
 RUN apt-get -y update && \
 	apt-get -y install \
+	parallel \
 	meson ninja-build \
 	sdcc \
 	lua5.3 liblua5.3-dev default-jre-headless openssh-server && \