Allow re-targeting of naclports install

libraries/jsoncpp-0.5.0/nacl-jsoncpp-0.5.0.sh

 #!/bin/bash
 # Copyright (c) 2012 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 
 # nacl-jsoncpp-0.5.0.sh
 #
 # usage:  nacl-jsoncpp-0.5.0.sh
 #
@@ skipping 23 matching lines @@
   ${NACLRANLIB} libjsoncpp.a
   set +x
 }
 
 
 CustomInstallStep() {
   Banner "Installing ${PACKAGE_NAME}"
   export PACKAGE_DIR="${NACL_PACKAGES_REPOSITORY}/${PACKAGE_NAME}"
 
   set -x
-  cp ${PACKAGE_DIR}/libjsoncpp.a ${NACL_SDK_USR_LIB}
-  cp -R ${PACKAGE_DIR}/include/json ${NACL_SDK_USR_INCLUDE}
+  cp ${PACKAGE_DIR}/libjsoncpp.a ${NACLPORTS_LIBDIR}
+  cp -R ${PACKAGE_DIR}/include/json ${NACLPORTS_INCLUDE}
   set +x
 }
 
 
 CustomPackageInstall() {
   DefaultPreInstallStep
   DefaultDownloadStep
   DefaultExtractStep
   CustomBuildStep
   CustomInstallStep
   DefaultCleanUpStep
 }
 
 CustomPackageInstall
 exit 0