RTTI support in devel/llvm40 (and maybe other llvm ports)

[Alexey Dokuchaev]

Hi Brooks,

I've just found out that our `devel/llvm40' port comes without
-DLLVM_ENABLE_RTTI=ON on the CMAKE_ARGS.  This is a regression
from e.g. 3.4 times when it was enabled by default.

The problem is that RTTI support is required by some consumers,
e.g. `graphics/openshadinglanguage' and `graphics/appleseed'
(cf. https://github.com/appleseedhq/appleseed/issues/1625),
but I cannot enable RTTI in those ports unless I enable it in
LLVM port(s) first.

The patch is very simple (apart port revision bump):

@@ -39,7 +41,7 @@
 SUB_LIST=	LLVM_PREFIX="${LLVM_PREFIX}" LLVM_SUFFIX="${LLVM_SUFFIX}"
 CMAKE_INSTALL_PREFIX=  ${LLVM_PREFIX}
-CMAKE_ARGS=	-DLLVM_BUILD_LLVM_DYLIB=ON
+CMAKE_ARGS=	-DLLVM_BUILD_LLVM_DYLIB=ON -DLLVM_ENABLE_RTTI=ON

Could you review/commit it, and check if other LLVM ports could
also benefit from it?  Thanks,

./danfe