Allow re-targeting of naclports install

examples/graphics/xaos/nacl-xaos.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-xaos.sh
 #
 # usage:  nacl-xoas.sh
 #
@@ skipping 30 matching lines @@
                   -Wl,--undefined=PPP_InitializeModule \
                   -Wl,--undefined=original_main"
   if [ ${NACL_ARCH} = "pnacl" ] ; then
     export CFLAGS="${CFLAGS} -O3"
     export LDFLAGS="${LDFLAGS} -O0 -static"
   else
      export CFLAGS="${CFLAGS} -O2"
   fi
   export AR=${NACLAR}
   export RANLIB=${NACLRANLIB}
-  export PKG_CONFIG_PATH=${NACL_SDK_USR_LIB}/pkgconfig
-  export PKG_CONFIG_LIBDIR=${NACL_SDK_USR_LIB}
+  export PKG_CONFIG_PATH=${NACLPORTS_LIBDIR}/pkgconfig
+  export PKG_CONFIG_LIBDIR=${NACLPORTS_LIBDIR}
 
-  export LIBS="-L${NACL_SDK_USR_LIB} -lppapi -lpthread -lstdc++ -lm -lnosys"
+  export LIBS="-L${NACLPORTS_LIBDIR} -lppapi -lpthread -lstdc++ -lm -lnosys"
 
   CONFIG_FLAGS="--with-png=no \
       --with-long-double=no \
       --host=nacl \
       --with-x11-driver=no \
       --with-sffe=no"
 
   ChangeDir ${NACL_PACKAGES_REPOSITORY}/${PACKAGE_NAME}
 
   # xaos does not work with a build dir which is separate from the
@@ skipping 36 matching lines @@
   DefaultBuildStep
   if [ ${NACL_ARCH} = "pnacl" ] ; then
     DefaultTranslateStep ${PACKAGE_NAME} ${PACKAGE_NAME}-build/bin/xaos
   fi
   CustomInstallStep
   DefaultCleanUpStep
 }
 
 CustomPackageInstall
 exit 0