added custom apptainer image slim

.gitlab-ci.yml

 image:
-  name: quay.io/singularity/singularity:v3.11.4-slim
+  # different images / but all should be comparable
+  # name: harbor.wolke.img.univie.ac.at/apptainer/singularity:v3.11.4-slim
+  name: harbor.wolke.img.univie.ac.at/apptainer/apptainer:v1.2.2
   entrypoint: ["/bin/sh", "-c"]
 
 variables:
   SFILE:
-    description: "file path of Singularity recipe file"
-    value: definition-files/Singularity.almalinux.base
+    description: "filename of Singularity recipe in definition-files"
+    value: Singularity.almalinux.base
   CONTAINERTAG:
     description: "registry name and tag, e.g. almalinux8:base"
     value: almalinux8:base
@@ -23,4 +25,4 @@ build:
     when: on_success
     expire_in: 1 day
     paths:
-      - $SFILE.sif
+      - definition-files/$SFILE.sif

Dockerfile

+FROM golang:1.20.0-alpine as builder
+
+################################################################################
+#
+# Copyright (C) 2019-2023 Vanessa Sochat. Modified by Michael Blaschek.
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or (at your
+# option) any later version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public
+# License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#
+################################################################################
+
+# alpine image with the go tools
+
+RUN apk update && \
+    apk add --virtual automake build-base linux-headers libffi-dev
+RUN apk add --no-cache bash git openssh gcc squashfs-tools sudo libtool gawk cryptsetup glib-dev
+RUN apk add --no-cache linux-headers build-base openssl-dev util-linux util-linux-dev shadow-uidmap libseccomp-dev
+
+ENV APPTAINER_VERSION=1.2.2
+LABEL Maintainer @mblaschek
+RUN wget -qO- https://github.com/apptainer/apptainer/releases/download/v${APPTAINER_VERSION}/apptainer-${APPTAINER_VERSION}.tar.gz | \
+    tar xzv && \
+    cd apptainer-${APPTAINER_VERSION} && \
+    ./mconfig -p /usr/local/apptainer && \
+    make -C builddir && \
+    make -C builddir install
+
+# See https://docs.docker.com/develop/develop-images/multistage-build/
+# for more information on multi-stage builds.
+FROM alpine:3.17
+LABEL Maintainer @mblaschek
+COPY --from=builder /usr/local/apptainer /usr/local/apptainer
+RUN apk add --no-cache ca-certificates libseccomp squashfs-tools tzdata bash && \
+    cp /usr/share/zoneinfo/UTC /etc/localtime
+ENV PATH="/usr/local/apptainer/bin:$PATH"
+ENTRYPOINT ["/usr/local/apptainer/bin/singularity"]