security/klee: Do not build on i386, it is unsupported upstream.

While here, add BACKEND multigroup and move STP and Z3 options there.

security/klee/Makefile

@@ -11,6 +11,8 @@ COMMENT=	Symbolic virtual machine built on top of LLVM
 LICENSE=	NCSA
 LICENSE_FILE=	${WRKSRC}/LICENSE.TXT
 
+NOT_FOR_ARCHS=	i386
+
 BUILD_DEPENDS=	llvm-config${LLVM_DEFAULT}:devel/llvm${LLVM_DEFAULT} \
 		gmake:devel/gmake
 # Should be a LIB_DEPEND, but hard to express in a generic manner
@@ -28,8 +30,10 @@ CMAKE_ARGS=	-DLLVM_CONFIG_BINARY=${LOCALBASE}/bin/llvm-config${LLVM_DEFAULT} \
 		-DMAKE_BINARY=${LOCALBASE}/bin/gmake
 
 # TODO METASMT
-OPTIONS_DEFINE=		TCMALLOC Z3 STP
+OPTIONS_DEFINE=		TCMALLOC
 OPTIONS_DEFAULT=	TCMALLOC Z3 STP
+OPTIONS_MULTI=		BACKEND
+OPTIONS_MULTI_BACKEND=	Z3 STP
 
 TCMALLOC_DESC=		Use tcmalloc library for memory management
 TCMALLOC_CMAKE_BOOL=	ENABLE_TCMALLOC