gitea: use gitea Makefile, fix builtin static files

[teutat3s]

This implements changes in the upstream build process and fixes the missing builtin static files in recent versions.

• Most important change is adding the missing bindata tag to GO_TAGS for integrating static files into the binary, see upstream "install from source" docs
• Switch from go to gmake and gitea's Makefile for building the package
• Added small patch to fix LDFLAGS where they shouldn't be
• nodejs and npm added as build dependencies
• VERSION file is used in the gitea's Makefile for baking the correct version into the binary

[jperkin]

Thanks! I've committed this now with a few changes:

• No need to manually update the $NetBSD$ lines, CVS handles those.

• I removed the dependencies on nodejs/npm and instead added a target to pre-generate the frontend files that can be downloaded separately at build time. We try very hard to avoid packages downloading files by themselves during builds.

• I didn't enable the bindata option as the documentation actually recommended against it for production environments. If at some point we decide that it might be useful to enable then it should probably go behind its own option. In any case adding it behind the sqlite option is incorrect.

Otherwise a pretty good first attempt, thanks a lot for the update, I'm sure users will appreciate having a working UI ;-)

[teutat3s]

Thanks a lot for the feedback and for improving my PR with your commit!

What would be the commands needed for uploading the frontend bits to LOCAL_PORTS?

How would I use CVS for finalizing a theoretically complete and fine PR?