Add sane compiler defaults for Asp's backends

[shoaibkamil]

For each of icc, gcc, etc., we should have two sets of default compiler flags: one for debug, and one for production/optimized compilation.

Est time: O(days).

[chiaracoetzee]

This involves at least two tasks: one is formulating the right set of default compiler flags for debug and release mode for each tool, and the other is designing the interface (how you instruct Asp to build for debug or for release). Under what scenarios should it default to debug or release?