Revert.

No, you cannot. It breaks build with read-only tree, for instance.
Noticed by Taylor Campbell on IRC.

lang/squeak-vm/Makefile

@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.22 2013/04/06 15:46:36 rodent Exp $
+# $NetBSD: Makefile,v 1.23 2013/04/08 16:45:33 asau Exp $
 #
 
 SQUEAK_VERSION=	4.10.2.2614
@@ -22,7 +22,7 @@ USE_LANGUAGES=	c c++
 USE_CMAKE=	yes
 USE_TOOLS=	gzip
 
-CONFIGURE_DIRS=	build
+CONFIGURE_DIRS=	${WRKSRC}/build
 CMAKE_ARG_PATH=	../unix
 #CMAKE_ARGS+=	-DCMAKE_VERBOSE_MAKEFILE:BOOL=TRUE	# debug
 CMAKE_ARGS+=	-DPKGMANDIR=${PKGMANDIR}