In devel/llvm-devel the first CMAKE_ARGS is overwritten like this
so -DLLVM_BUILD_LLVM_DYLIB=ON is never passed to the build. Currently
llvm-devel does not appear to build a libLLVM.so. Is this deliberate?
Can the first CMAKE_ARGS be removed or should it be passed through
to the build?
A commit references this bug:
Date: Wed Jan 9 23:06:08 UTC 2019
New revision: 489840
Upgrade to a new snapshot.
Fix a bug that resulted in LLVM_BUILD_LLVM_DYLIB not being passed as a
cmake argument. 
PR: 234739 
Submitted by: tobik 
Thanks for the report!