If TRICK_HOME is not set then ICG fails to run correctly. ICG calls
${TRICK_HOME}/bin/trick-gte to get some environment information.
Set TRICK_HOME for the ICG command in the CMakeLists.txt
Updated minimum cmake version to 3.1
Added checks in findllvm script to handle old 3.4 LLVM version
Added back include directories needed by old LLVM version in ICG.
* Merging changes from cmake branch to master
* Fixing includes for renamed header files
* still need build rule
* Adding warning for swig code for gcc8+
* Adding CMakeLists.txt for data products
* Cmake merge #901
Making adjustments to get cmake working on the Mac (Mojave)
* Cmake merge #901
Changing string append to list append
