Work around broken cross-build of x11/libxcb.

The right fix requires more knowledge of pkg-config than I have at
the moment.

Index: x11/libxcb/Makefile
===================================================================
RCS file: /cvsroot/pkgsrc/x11/libxcb/Makefile,v
retrieving revision 1.20
diff -p -u -r1.20 Makefile
--- x11/libxcb/Makefile	1 Feb 2013 14:40:29 -0000	1.20
+++ x11/libxcb/Makefile	23 Apr 2013 13:29:24 -0000
@@ -11,8 +11,8 @@ HOMEPAGE=	http://xcb.freedesktop.org/
 COMMENT=	X protocol C-language Binding
 LICENSE=	mit # with no-advertising clause
 
-BUILD_DEPENDS+=	libxslt>=1.1.0:../../textproc/libxslt
-BUILD_DEPENDS+= ${PYPKGPREFIX}-xcbgen>=1.7:../../x11/py-xcbgen
+TOOL_DEPENDS+=	libxslt>=1.1.0:../../textproc/libxslt
+TOOL_DEPENDS+=	${PYPKGPREFIX}-xcbgen>=1.7:../../x11/py-xcbgen
 
 GNU_CONFIGURE=	yes
 USE_LIBTOOL=	yes
@@ -21,6 +21,19 @@ USE_TOOLS+=	gmake pkg-config
 CONFIGURE_ARGS+=	--disable-build-docs	# or needs doxygen
 CONFIGURE_ARGS+=	--disable-doxygen
 
+.include "../../mk/bsd.prefs.mk"
+
+.if !empty(USE_CROSS_COMPILE:M[yY][eE][sS])
+# [TRC 20130328: XXX This is kludgerific!  We need to use the full
+# pathname in the host to the target's xcbincludedir, but libxcb gets
+# that from pkg-config, which reports the pathname in the target.]
+SUBST_CLASSES+=			xcbincludedir
+SUBST_FILES.xcbincludedir+=	src/Makefile.in
+SUBST_MESSAGE.xcbincludedir=	Use the xcbincludedir in the cross destdir.
+SUBST_STAGE.xcbincludedir=	pre-configure
+SUBST_SED.xcbincludedir=	-e s,'$$(XCBPROTO_XCBINCLUDEDIR)',${CROSS_DESTDIR:Q}'&',g
+.endif
+
 # Adds -Wl,-R to pkgconfig files automatically
 PKGCONFIG_OVERRIDE+=	xcb-composite.pc.in
 PKGCONFIG_OVERRIDE+=	xcb-damage.pc.in