Allow re-targeting of naclports install

libraries/fftw-3.2.2/nacl-fftw-3.2.2.sh

Index: libraries/fftw-3.2.2/nacl-fftw-3.2.2.sh
diff --git a/libraries/fftw-3.2.2/nacl-fftw-3.2.2.sh b/libraries/fftw-3.2.2/nacl-fftw-3.2.2.sh
index 5dfffbd24e58073f1b715df3c88e3cb4bf8b23b3..80d80f66ff8f63d9e658c044449cec9efe18ed88 100755
--- a/libraries/fftw-3.2.2/nacl-fftw-3.2.2.sh
+++ b/libraries/fftw-3.2.2/nacl-fftw-3.2.2.sh
@@ -25,8 +25,8 @@ CustomConfigureStep() {
   export CXX=${NACLCXX}
   export AR=${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=${NACLPORTS_LIBDIR}
   export PATH=${NACL_BIN_PATH}:${PATH};
   ChangeDir ${NACL_PACKAGES_REPOSITORY}/${PACKAGE_NAME}
   if [ ${NACL_ARCH} = "pnacl" ] ; then
@@ -35,7 +35,7 @@ CustomConfigureStep() {
     extra="--enable-sse2"
   fi
 
-  ./configure --prefix=${NACL_SDK_USR} --host=nacl ${extra}
+  ./configure --prefix=${NACLPORTS_PREFIX} --host=nacl ${extra}
 }