Does it work like this?
Index: Makefile
===================================================================
RCS file: /cvs/ports/devel/llvm/Makefile,v
retrieving revision 1.52
diff -u -p -r1.52 Makefile
--- Makefile 31 Aug 2012 16:21:20 -0000 1.52
+++ Makefile 4 Sep 2012 23:44:23 -0000
@@ -10,7 +10,7 @@ COMMENT = modular, fast C/C++/ObjC compi
LLVM_V = 3.1
DISTNAME = llvm-${LLVM_V}.src
PKGNAME = llvm-${LLVM_V}
-REVISION = 7
+REVISION = 8
CATEGORIES = devel
# packager notes in http://llvm.org/docs/Packaging.html
@@ -53,10 +53,10 @@ REGRESS_FLAGS = RUNTESTFLAGS=
SEPARATE_BUILD = Yes
USE_LIBTOOL = Yes
-MAKE_ENV = REQUIRES_RTTI=1
CONFIGURE_STYLE = cmake
CONFIGURE_ARGS = -DLLVM_ENABLE_FFI:Bool=False \
+ -DLLVM_REQUIRES_RTTI:Bool=True \
-DCMAKE_BUILD_TYPE:String=Release
CLANG_INCLUDE_PATH = lib/clang/${LLVM_V}/include
