Add top level build script for building packages.

ports/glibc-compat/build.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.
 
-source pkg_info
-source ../../build_tools/common.sh
-
 readonly LIB_GLIBC_COMPAT=libglibc-compat.a
 
-ExtractStep() {
-  ChangeDir ${NACL_PACKAGES_REPOSITORY}
-  MakeDir ${PACKAGE_NAME}
-  LogExecute cp -rf ${START_DIR}/* ${PACKAGE_NAME}
-}
+BUILD_DIR=${SRC_DIR}
 
 ConfigureStep() {
   Banner "Configuring ${PACKAGE_NAME}"
+  MakeDir ${BUILD_DIR}
+  LogExecute cp -rf ${START_DIR}/* ${BUILD_DIR}
   # export the nacl tools
   export CC=${NACLCC}
   export CXX=${NACLCXX}
   export AR=${NACLAR}
   export NACL_SDK_VERSION
-  ChangeDir ${NACL_PACKAGES_REPOSITORY}/${PACKAGE_NAME}
+  ChangeDir ${SRC_DIR}
   LogExecute rm -rf out
 }
 
 InstallStep() {
   Remove ${NACLPORTS_LIBDIR}/${LIB_GLIBC_COMPAT}
   Remove ${NACLPORTS_INCLUDE}/glibc-compat
   LogExecute install -m 644 out/${LIB_GLIBC_COMPAT} ${NACLPORTS_LIBDIR}/${LIB_GLIBC_COMPAT}
   LogExecute cp -r include ${NACLPORTS_INCLUDE}/glibc-compat
 }
-
-PackageInstall
-exit 0