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