Fix manual devcontainer workflow on Linux

This ensures that devcontainer can be built and manually run.

Signed-off-by: eriknordmark <erik@zededa.com>

.devcontainer/Dockerfile

@@ -17,7 +17,7 @@ RUN arch=$(uname -m); \
   unzip protobuf.zip -d /usr/local; \
   rm -f protobuf.zip
 
-ADD https://github.com/seamia/protodot.git /protodot
+RUN git clone https://github.com/seamia/protodot.git /protodot
 RUN go build -C /protodot -o /usr/local/bin/protodot .
 
 RUN mkdir -p $(go env GOPATH)

README.md

@@ -103,6 +103,21 @@ devcontainer --workspace-folder . up
 devcontainer exec --workspace-folder . make proto
 ```
 
+#### Manual ad-hoc use of devcontainer on Linux
+
+First the devcontainer needs to be built specifying the TARGETOS:
+```bash
+docker build -f .devcontainer/Dockerfile --build-arg TARGETOS=linux .
+```
+
+Then the produced container (hash) can be invoked and make run:
+```bash
+docker run --network=host -it -v $PWD:/home d9ca10a77a8c
+cd home
+make proto
+exit
+```
+
 #### Local
 
 If running locally, you need to install the prerequisites yourself.