Add zeek -V/--build-info

This adds a new utility called ci/collect-repo-info.py to produce a JSON
document that is then baked into the Zeek executable file. Further, when
creating a tarball via `make dist`, put a top-level repo-info.json file
in place that is picked when no .git directory exists.

Closes #1405

src/Options.h

@@ -32,6 +32,7 @@ struct Options
 	void filter_supervised_node_options();
 
 	bool print_version = false;
+	bool print_build_info = false;
 	bool print_usage = false;
 	bool print_execution_time = false;
 	bool print_signature_debug_info = false;