Skip rebuilds if nothing has changed

[davewasmer]

There might be many instances where the developer runs denali server with nothing changed from the last build. It would be ideal if we could simply skip the build step and re-use the already compiled dist.

We could hash the source directories (do we include node_modules and/or addons?) at build time, and write that hash to dist/.build (filename TBD). Then when we go to rebuild, we rehash the source directories and compare to dist/.build. If they are the same, we are okay to re-use the built output.

This might also be helpful when we get around to implementing a denali server --production that works on prebuilt files

[seawatts]

This sounds amazing!