Eglide: more decent C compile and debug environment

Summary:
To build, we add clang/llvm and CMake.

To debug, we add strace and valgrind.

Fixes T868.

Test Plan: salt eglide state.highstate, test apps

Reviewers: Sandlayth

Maniphest Tasks: T868

Differential Revision: http://devcentral.nasqueron.org/D403