Use make flag to control unified layout compiler flags

[compor]

This PR:

• Adds the use of UNMODIFIED makefile definition to disable all UnASL-related modifications in the LLVM/Clang compiler toolchain controlled by flags. The flag can be added and turned on to makefile definitions file that invoke an unmodified compiler toolchain.

Limitation: In order for compilation to occur correctly, this is only supported for the init make target. A future patch is needed to also disable the UnASL-related makefile rules.

[blackgeorge-boom]

Does the work for now. LGTM