Add a module to allow for easier building of a port using CLang/LLVM

by adding MODULES=lang/clang. Based on gcc4.port.mk and simplified.
OK robert@

lang/clang/clang.port.mk

@@ -0,0 +1,30 @@
+# $OpenBSD: clang.port.mk,v 1.1.1.1 2012/04/05 18:28:16 sthen Exp $
+
+MODCLANG_ARCHS ?=
+MODCLANG_LANGS ?=
+
+.if !${MODCLANG_LANGS:L:Mc}
+# Always include support for this
+MODCLANG_LANGS += c
+.endif
+
+_MODCLANG_OKAY = c c++
+.for _l in ${MODCLANG_LANGS:L}
+.  if !${_MODCLANG_OKAY:M${_l}}
+ERRORS += "Fatal: unknown language ${_l}"
+.  endif
+.endfor
+
+BUILD_DEPENDS += devel/llvm
+_MODCLANG_LINKS = clang gcc clang cc
+
+.if ${MODCLANG_LANGS:L:Mc++}
+_MODCLANG_LINKS += clang++ g++ clang++ c++
+.endif
+
+.if !empty(_MODCLANG_LINKS)
+.  for _src _dest in ${_MODCLANG_LINKS}
+MODCLANG_post-patch += ln -sf ${LOCALBASE}/bin/${_src} ${WRKDIR}/bin/${_dest};
+.  endfor
+.endif
+