add el8 container builds

.gitlab-ci-el8.Dockerfile

+FROM igwn/base:el8-testing
+
+LABEL name="LALSuite Nightly - EL8" \
+      maintainer="Adam Mercer <adam.mercer@ligo.org>" \
+      support="Reference Platform"
+
+# add RPMs to container
+COPY rpms /rpms
+
+# install latest release
+RUN dnf -y -q upgrade && \
+      dnf -y -q install createrepo && \
+      createrepo --quiet /rpms && \
+      dnf clean all
+
+# generate repo metadata
+RUN echo "[local-builds]" > /etc/yum.repos.d/local-builds.repo && \
+    echo "name=Local builds" >> /etc/yum.repos.d/local-builds.repo && \
+    echo "baseurl=file:///rpms" >> /etc/yum.repos.d/local-builds.repo && \
+    echo "enabled=1" >> /etc/yum.repos.d/local-builds.repo && \
+    echo "gpgcheck=0" >> /etc/yum.repos.d/local-builds.repo
+
+# install packages from local repo
+RUN dnf -y install lal* python*-lal --exclude lalsuite* && \
+      dnf clean all

.gitlab/ci/containers.yml

@@ -79,6 +79,22 @@
     - lalpulsar:rpm-el7
     - lalapps:rpm-el7
 
+.docker:el8:
+  variables:
+    DOCKER_FILE: ".gitlab-ci-el8.Dockerfile"
+  extends:
+    - .docker:el
+  needs:
+    - lal:rpm-el8
+    - lalframe:rpm-el8
+    - lalmetaio:rpm-el8
+    - lalsimulation:rpm-el8
+    - lalburst:rpm-el8
+    - lalinspiral:rpm-el8
+    - lalinference:rpm-el8
+    - lalpulsar:rpm-el8
+    - lalapps:rpm-el8
+
 # template for Debian docker builds
 .docker:debian:
   extends:
@@ -116,7 +132,7 @@
     - !reference [.ci-koji, rules]
     - !reference [.ci-nightly-deploy, rules]
 
-# build a nightly container from the RPMs
+# build nightly containers from the RPMs
 docker:nightly:el7:
   before_script:
     - !reference [.container_snippets, nightly_image]
@@ -125,7 +141,15 @@ docker:nightly:el7:
     - .docker:el7
     - .docker:nightly
 
-# build a tagged container from the rpms
+docker:nightly:el8:
+  before_script:
+    - !reference [.container_snippets, nightly_image]
+    - !reference [.container_snippets, rhel]
+  extends:
+    - .docker:el8
+    - .docker:nightly
+
+# build tagged containers from the rpms
 docker:tags:el7:
   before_script:
     - !reference [.container_snippets, tag_image]
@@ -134,6 +158,14 @@ docker:tags:el7:
     - .docker:el7
     - .docker:tags
 
+docker:tags:el8:
+  before_script:
+    - !reference [.container_snippets, tag_image]
+    - !reference [.container_snippets, rhel]
+  extends:
+    - .docker:el8
+    - .docker:tags
+
 # build a nightly container for Debian bullseye
 docker:nightly:bullseye:
   before_script: