Add Dockerfile with hamnet70 build dependencies

ci/docker/impl/Dockerfile

@@ -0,0 +1,11 @@
+FROM debian:stable
+
+# for Forgejo Actions
+RUN apt update && apt install -y --no-install-recommends nodejs git && apt clean
+
+# Hamnet70 build dependencies
+RUN apt install -y --no-install-recommends cmake make gcc libc-dev libliquid-dev libhackrf-dev libfec-dev libfftw3-dev && apt clean
+
+# run as unprivileged user in the container
+RUN useradd -m ciuser
+USER ciuser

ci/docker/impl/build.sh

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+#!/bin/sh
+
+if [ -z "$1" ]; then
+	echo "usage: $0 <tag-version>"
+	exit 1
+fi
+
+docker build -t git.tkolb.de/amateurfunk/hamnet70/impl_buildenv:$1 .

ci/docker/impl/test.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+if [ -z "$1" ]; then
+	echo "usage: $0 <tag-version>"
+	exit 1
+fi
+
+docker run -v $(realpath ../../../impl):/impl -it git.tkolb.de/amateurfunk/hamnet70/impl_buildenv:$1

ci/docker/impl/upload.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+
+if [ -z "$1" ]; then
+	echo "usage: $0 <tag-version>"
+	exit 1
+fi
+
+docker login
+docker push git.tkolb.de/amateurfunk/hamnet70/impl_buildenv:$1
+docker logout