allow different dockerfile location

[MichaelBitard]

I have a particular use case, but not so particular when it comes to docker.

I'm building an addon for signal and I'd like to automate the image construction using this builder.
The problem is, with the latest versions of signal, it's not possible to build non 64 bits versions anymore using alpine. That means that I end up with 2 dockerfiles, one for the amd64 and arch64 architectures, and one for the others.

It could be solved by adding an argument to specify the dockerfile location (the equivalent to option -f, --file string Name of the Dockerfile (Default is 'PATH/Dockerfile') in docker build) in this actions' args.

What do you think? I could make a PR about it.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.