Add top level build script for building packages.

ports/OpenSceneGraph/build.sh

Index: ports/OpenSceneGraph/build.sh
diff --git a/ports/OpenSceneGraph/build.sh b/ports/OpenSceneGraph/build.sh
old mode 100755
new mode 100644
index 5b49f019865731487a2d025f95915feda06cb6fb..72ded7c7a3063d6cdea88d310871e1284aa1f7d9
--- a/ports/OpenSceneGraph/build.sh
+++ b/ports/OpenSceneGraph/build.sh
@@ -3,11 +3,13 @@
 # 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() {
-  Banner "Configuring ${PACKAGE_NAME}"
+  Banner "No configure step"
+}
+
+BuildStep() {
   # export the nacl tools
   export CC=${NACLCC}
   export CXX=${NACLCXX}
@@ -20,10 +22,10 @@ ConfigureStep() {
   export LIB_OSG=libosg.a
   export LIB_OSGUTIL=libosgUtil.a
   export LIB_OPENTHREADS=libOpenThreads.a
-
-  ChangeDir ${NACL_PACKAGES_REPOSITORY}/${PACKAGE_NAME}
+  DefaultBuildStep
 }
 
+
 InstallStep() {
   Remove ${NACLPORTS_INCLUDE}/osg
   Remove ${NACLPORTS_INCLUDE}/osgUtil
@@ -39,7 +41,3 @@ InstallStep() {
   install -m 644 ${LIB_OSGUTIL} ${NACLPORTS_LIBDIR}/${LIB_OSGUTIL}
   install -m 644 ${LIB_OPENTHREADS} ${NACLPORTS_LIBDIR}/${LIB_OPENTHREADS}
 }
-
-
-PackageInstall
-exit 0