tools: add compile_commands.json gyp generator

this is a re-base of the gyp part of
3c46bb99
after bumping GYP version to
https://chromium.googlesource.com/external/gyp/+/eb296f67da078ec01f5e3a9ea9cdc6d26d680161



Original-Review-By: James M Snell <jasnell@gmail.com>
Ref: https://github.com/nodejs/node/pull/7986
PR-URL: https://github.com/nodejs/node/pull/12450


Reviewed-By: João Reis <reis@janeasystems.com>