Investigate memory usage during build

[davewasmer]

There are reports (from @seawatts) that Denali apps with multiple on-the-fly compiling addons (not sure if that's relevant) end up using more than Heroku's 700mb memory limit, resulting in the dyno getting killed before launching.

We figure out why the heck Denali is using > 700mb of memory to build.

[seawatts]

This might not be an actual issue. But I haven't confirmed. I believe that it might have been a coincidence that Heroku was spinning up the instance at the same time it was trying to build.