RegEx - CodeGen - reestablish -O4 option for clang invocation

The issue turns out to be a bug in the installation of clang and
llvm on debian.  clang passes a path for the LLVMGold plugin that
is incorrect.  Also:  LLVMGold has a reference to the LTO library
that does not resolve correctly.  Just placing links to the expected
locations that point to the actual locations of these libraries
solves this problem.  This issue will hopefully be cleaned up in
newer versions of debian and derived distributions.