[frdb] Add BUILD.gn file. (#17673)
[frdb] Add BUILD.gn file. (#17673)

Adds fuchsia_remote_debug_protocol gn file.

tvolkert/flutter,Hixie/flutter,Hixie/flutter,Hixie/flutter,tvolkert/flutter,tvolkert/flutter,flutter/flutter,flutter/flutter,cbracken/flutter,cbracken/flutter,tvolkert/flutter,flutter/flutter,tvolkert/flutter,cbracken/flutter,cbracken/flutter,tvolkert/flutter,Hixie/flutter,cbracken/flutter,flutter/flutter,cbracken/flutter,tvolkert/flutter,cbracken/flutter,Hixie/flutter,Hixie/flutter,Hixie/flutter,tvolkert/flutter,cbracken/flutter,flutter/flutter,Hixie/flutter,flutter/flutter,Hixie/flutter,flutter/flutter,flutter/flutter,flutter/flutter,tvolkert/flutter,Hixie/flutter,cbracken/flutter,flutter/flutter,cbracken/flutter,tvolkert/flutter