Add top level build script for building packages.

ports/Mesa/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=${SRC_DIR}
 
 ConfigureStep() {
   # export the nacl tools
   export CC=${NACLCC}
   export CXX=${NACLCXX}
   export AR=${NACLAR}
   export LD=${NACLLD}
   export RANLIB=${NACLRANLIB}
   export PKG_CONFIG_PATH=${NACLPORTS_PREFIX}/lib/pkgconfig
   export PKG_CONFIG_LIBDIR=${NACLPORTS_PREFIX}/lib
   export PATH=${NACL_BIN_PATH}:${PATH};
   export X11_INCLUDES=
-  ChangeDir ${NACL_PACKAGES_REPOSITORY}/${PACKAGE_NAME}
+  ChangeDir ${BUILD_DIR}
   ./configure \
     --host=nacl \
     --enable-static \
     --prefix=${NACLPORTS_PREFIX} \
     --exec-prefix=${NACLPORTS_PREFIX} \
     --libdir=${NACLPORTS_PREFIX}/lib \
     --oldincludedir=${NACLPORTS_PREFIX}/include \
     --datarootdir=${NACLPORTS_PREFIX} \
     --disable-gl-osmesa \
     --with-x=no \
     --with-driver=osmesa \
     --disable-asm \
     --disable-glut \
     --disable-gallium \
     --disable-egl \
     --disable-glw
 }
 
 
 InstallStep() {
   # assumes pwd has makefile
   make install
 }
-
-
-PackageInstall
-exit 0