cmake: add PROFILING option
cmake: add PROFILING option

All to profile the binary with -pg -O1 when calling cmake with
-DPROFILING=ON. The above options will be added to compilation and linking,
and stripping the release build artifacts will be disabled in this case.

Profiling allows to perform a few micro optimizations of the code base and
judge the usefulness of changes in the solver.

nmanthey/riss-solver,nmanthey/riss-solver,nmanthey/riss-solver