Build from source 100x slower than prod

[thaas]

I just rebased onto master, re-built, and still getting about 1100 H/s with scrypt vs. 1100 kH/s from the executable from the website (with no changes to the scrypt implementation, just using that as a benchmark for my own algorithm). So marginally faster but still, build is very very slow compared to the production version, with zero changes to the algorithm.