Use clang on OpenBSD

Makefile

@@ -17,8 +17,8 @@ ifeq ($(OSTYPE),FreeBSD)
 	include make-bsd.mk
 endif
 ifeq ($(OSTYPE),OpenBSD)
-	CC=egcc
-	CXX=eg++
+	CC=clang
+	CXX=clang++
 	ZT_BUILD_PLATFORM=9
 	include make-bsd.mk
 endif