Allow re-targeting of naclports install

libraries/flac-1.2.1/nacl-flac-1.2.1.sh

Index: libraries/flac-1.2.1/nacl-flac-1.2.1.sh
diff --git a/libraries/flac-1.2.1/nacl-flac-1.2.1.sh b/libraries/flac-1.2.1/nacl-flac-1.2.1.sh
index 6380c6e6b6d59b60df830b71b59473c35b13d782..52a78e079c7c0c59b0398b0f74b619d62ba3bce9 100755
--- a/libraries/flac-1.2.1/nacl-flac-1.2.1.sh
+++ b/libraries/flac-1.2.1/nacl-flac-1.2.1.sh
@@ -22,8 +22,8 @@ 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_PREFIX}/lib/pkgconfig
+  export PKG_CONFIG_LIBDIR=${NACLPORTS_PREFIX}/lib
   export PATH=${NACL_BIN_PATH}:${PATH};
   export LIBS="-lnosys"
   ChangeDir ${NACL_PACKAGES_REPOSITORY}/${PACKAGE_NAME}
@@ -33,10 +33,10 @@ CustomConfigureStep() {
   ../configure \
     --host=nacl \
     --disable-shared \
-    --prefix=${NACL_SDK_USR} \
-    --exec-prefix=${NACL_SDK_USR} \
-    --libdir=${NACL_SDK_USR}/lib \
-    --oldincludedir=${NACL_SDK_USR}/include \
+    --prefix=${NACLPORTS_PREFIX} \
+    --exec-prefix=${NACLPORTS_PREFIX} \
+    --libdir=${NACLPORTS_PREFIX}/lib \
+    --oldincludedir=${NACLPORTS_PREFIX}/include \
     --enable-sse \
     --disable-3dnow \
     --disable-altivec \