symbols: improvements to ctags build script
Created by: keegancsmith
The main improvement is we no longer ship the ctags build dependencies in the symbols docker image. Otherwise this can be reviewed commit by commit:
- remove seccomp support in ctags
- use all your cores to build ctags
- cleanup via trap for ctags-install-alpine
The cleanup of this script was motivated in wanting to share it with how we build ctags in zoekt.
Test Plan: built and ran the docker image locally. Verified that universal-ctags --help
didn't fail. Pushed this branch to backend integration.