Feature: Allow to pass cli options to LLVM

[v01dXYZ]

LLVM has a number of options that are used by its CLI tools for many purposes among:

• enable/disable some passes or features within a pass
• configure a pass with other parameters (depth analysis, ...)
• output intermediate steps (such as print before/after a pass)

This is configurable using ParseCommandLineOptions() which takes argc, argv[] or look at the env variable variable specified as argument.

It could be set up in llvm_context.cpp.