Improve docker build

[orgads]

• Use current code instead of cloning from github.
• Use multi-stage instead of deleting everything.

[davehorton]

Hmm this fails for me.

Also, I don't like the fact that now we have lost the ability to see the specific git tag that this was built from.

g++ -DHAVE_CONFIG_H -I. -I.. <...> -DDRACHTIO_VERSION=\"1.0.0\"

[orgads]

The failure is:

Killed signal terminated program cc1plus

I don't see how that's related to any of my changes.

[orgads]

How about now? You can build with ./build-docker.sh, and it should use the current version.

[orgads]

Rebased. @davehorton ping.