Add top level build script for building packages.

ports/fftw/build.sh

 #!/bin/bash
 # Copyright (c) 2011 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.
 
-source pkg_info
-source ../../build_tools/common.sh
+BUILD_DIR=${NACL_PACKAGES_REPOSITORY}/${PACKAGE_NAME}
 
 ConfigureStep() {
   local EXTRA_CONFIGURE_OPTS=("${@:-}")
   Banner "Configuring ${PACKAGE_NAME}"
   # Export the nacl tools.
   export CC=${NACLCC}
   export CXX=${NACLCXX}
   export AR=${NACLAR}
   export RANLIB=${NACLRANLIB}
   export PKG_CONFIG_PATH=${NACLPORTS_LIBDIR}/pkgconfig
   export PKG_CONFIG_LIBDIR=${NACLPORTS_LIBDIR}
   export PATH=${NACL_BIN_PATH}:${PATH};
-  ChangeDir ${NACL_PACKAGES_REPOSITORY}/${PACKAGE_NAME}
   extra="--enable-threads"
   if [ ${NACL_ARCH} = "x86_64" -o ${NACL_ARCH} = "i686" ]; then
     extra="${extra} --enable-sse2"
   fi
 
   LogExecute ./configure \
     --host=nacl \
     --prefix=${NACLPORTS_PREFIX} \
     ${EXTRA_CONFIGURE_OPTS[@]} \
     ${extra}
@@ skipping 14 matching lines @@
   ValidateStep
 
   # build fftwf (float)
   EXECUTABLES=tools/fftwf-wisdom${NACL_EXEEXT}
   ConfigureStep --enable-float
   BuildStep
   InstallStep
   TranslateStep
   ValidateStep
 }
-
-PackageInstall
-exit 0