releases/build.sh: Enforce amd64, use .containerversion

Currently it is not posisble to reproducibly build the firmware due to
the toolchains we have, therefore we enforce amd64.

We have recently added a file called .containerversion with the version
of the container that the project should build with. Let's tag the built
version in release/build.sh with that as well to make it easier work
with.

releases/build.sh

@@ -35,7 +35,10 @@ fi
 
 
 # Build the Docker image (this can take a while):
-docker build --pull --force-rm --no-cache -t bitbox02-firmware .
+#  The firmware is only reproducible with the same host compiler. For now we force linux/amd64.
+#  The file .containerversion does not exist in older versions of the project.
+containerversion=$(2>/dev/null cat .containerversion || echo "latest")
+docker build --pull --platform linux/amd64 --force-rm --no-cache -t bitbox02-firmware:${containerversion} .
 
 # Revert the above local patch to the Dockerfile again to have a clean state.
 git checkout -- Dockerfile
@@ -47,7 +50,7 @@ git checkout -- Dockerfile
 #
 # The safe.directory config is so that git commands work. even though the repo folder mounted in
 # Docker is owned by root, which can be different from the owner on the host.
-docker run -it --rm --volume `pwd`:/bb02 bitbox02-firmware bash -c "git config --global --add safe.directory /bb02 && cd /bb02 && $2"
+docker run -it --rm --volume `pwd`:/bb02 bitbox02-firmware:${containerversion} bash -c "git config --global --add safe.directory /bb02 && cd /bb02 && $2"
 
 echo "firmware.bin created at:"
 echo `pwd`/build/bin/firmware.bin