go-fuzz-build: generate an executable rather than a zip file

[josharian]

[broken out from discussion in #273]

It'd be better to do as std does with testing and emit an executable instead of a zip file and using an external runner.

Off the top of my head, steps for this:

• figure out how to have instrumented code live alongside regular code (test runner)
• make sonar instrumentation always present and controlled on a run by run basis
• do dynamic rather than static literal collection
• refactor everything to support this

I don't know how to do step one. The rest are non-trivial, but seem possible.