gitlab-ci: Explicitly install linux-libc-dev for foreign architectures

Something seems to have changed in Debian buster causing installation
of the other foreign packages to fail without this.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>

.gitlab-ci/debian-install.sh

@@ -88,6 +88,7 @@ for arch in $CROSS_ARCHITECTURES; do
     apt-get install -y \
             libdrm-dev:${arch} \
             libexpat1-dev:${arch} \
+            linux-libc-dev:${arch}/stretch-backports \
             libelf-dev:${arch}
 done
 apt-get install -y \