Change to release procedure: tag after build

[rvagg]

This is for @nodejs/build and also @chrisdickinson and @Fishrock123

During our last build convergence meeting @misterdjules mentioned that he tags after building releases for joyent/node. We currently tag before release as we use the tag name for the Jenkins build to both fetch the right commit and name the builds. Unfortunately on a few occasions we've had failed builds but because they were already tagged we had to bump the patch version after fixing and then build again. Ideally, the releaser should be able to push an arbitrary branch, run the build by specifying a commit, then if they decide that should be promoted as as a release version then they merge & tag at the same time as promoting.

This will require minor changes to our Jenkins setup and also some work similar to #1938 to make the Makefile and vcbuild.bat a little smarter (I think).

[chrisdickinson]

This would be awesome. Tagging after build would alleviate a lot of the stress I felt during the botched v1.8.0 release.

[Fishrock123]

👍

[Fishrock123]

This was done at some point. Closing.