Use expression evaluation as branching condition

[Naville]

Currently the branching condition used by Obfuscator-LLVM team is creating 1.0==1.0 always true compare predicate then obfuscate using a given expression at finalization part.

We could randomly generate a mathematical expression like 1+2-3*4 each time then build IRs on top of this as the LHS, then use tinyexpr to evaluate the result and build RHS on top of it