osmo-ggsn-latest: add more kernel build depends

Add everything needed to run ttcn3-ggsn-test-kernel-* jobs.
osmo-ggsn-master needs less dependencies, as more get installed in the
base image debian-stretch-build.

Related: OS#3208
Change-Id: Iaef87c3418b8e6f1e427b2abd9d40e9e28dc63e9

osmo-ggsn-latest/Dockerfile

@@ -24,11 +24,18 @@ RUN	ln -s /bin/true /usr/local/bin/update-initramfs && \
 	apt-get update && \
 	apt-get install -y --no-install-recommends \
 		bc \
+		bison \
 		bridge-utils \
 		busybox-static \
 		ca-certificates \
+		flex \
+		gcc \
+		git \
+		libc6-dev \
 		libelf-dev \
+		libssl-dev \
 		linux-image-amd64 \
+		make \
 		osmo-ggsn \
 		pax-utils \
 		qemu-system-x86 \