xbps: look for headers/libs in XBPS_MASTERDIR for the bootstrap build.

srcpkgs/xbps/template

@@ -12,7 +12,10 @@ license="Simplified BSD"
 
 bootstrap=yes
 
-if [ "$CHROOT_READY" ]; then
+if [ -z "$CHROOT_READY" ]; then
+	CFLAGS+=" -idirafter ${XBPS_MASTERDIR}/usr/include"
+	LDFLAGS+=" -L${XBPS_MASTERDIR}/usr/lib"
+else
 	hostmakedepends="which pkg-config"
 	makedepends+=" atf-devel"
 	configure_args+=" --enable-tests"