ci: Use Hadolint linter for Dockerfile, revert workflow to pull_request

Workflows running on pull_request_target events run in the context of
the base of the pull request, meaning that the Docker image is built
from the base and not from the merge commit. This is not what we want.
Revert to pull_request instead.

For the linter action that we used, this means that the workflow will
fail when running from fork. There is a related issue on the Action's
repository, but it seems to get very little activity. Let's switch to
something that looks better maintained, and that does not have issues
with running from forks.

Let's address the reports raised by the new linter, Hadolint.

Fixes: 7daff43 ("ci: Run Docker CI job on pull_request_target instead of pull_request")
Signed-off-by: Quentin Monnet <[email protected]>

Author: qmonnet

.github/workflows/docker.yaml

@@ -1,7 +1,7 @@
 name: docker
 
 on:
-  pull_request_target: {}
+  pull_request: {}
   push:
     branches:
       - master
@@ -29,8 +29,6 @@ jobs:
           docker run --rm --privileged --pid=host bpftool map
 
       - name: Lint Docker image
-        uses: luke142367/Docker-Lint-Action@5c4c86226f39785a66827bbc2e322600c9afa3a9
+        uses: hadolint/hadolint-action@54c9adbab1582c2ef04b2016b760714a4bfde3cf
         with:
-          target: Dockerfile
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          dockerfile: Dockerfile

Dockerfile

@@ -3,6 +3,8 @@
 # And then use it:
 #     $ docker run --rm -ti --privileged --pid=host bpftool prog
 
+# hadolint global ignore=DL3008
+
 FROM ubuntu:22.04 as builder
 
 RUN \
@@ -19,9 +21,9 @@ RUN \
 	rm -rf /var/lib/apt/lists/*
 
 COPY . /src
-RUN cd /src/src && \
-	make clean && \
-	make -j $(nproc)
+RUN \
+	make -C /src/src clean && \
+	make -C /src/src -j "$(nproc)"
 
 FROM ubuntu:22.04
 RUN \