Add top level build script for building packages.

ports/drod/build.sh

Index: ports/drod/build.sh
diff --git a/ports/drod/build.sh b/ports/drod/build.sh
old mode 100755
new mode 100644
index 706296bc68a2f9d0af3dd0e94fe802c5bbdf0568..9fa4a9d4c8dc804d677a61524b33e096cb2597cc
--- a/ports/drod/build.sh
+++ b/ports/drod/build.sh
@@ -3,13 +3,11 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-source pkg_info
-
 PACKAGE_DIR=drod-213fa477000429fb9a5f4a77673394d47cadbfac
-source ../../build_tools/common.sh
-
-export DESTDIR=${PUBLISH_DIR}/.data
 EXECUTABLES=custom/bin/drod
+BUILD_DIR=${NACL_PACKAGES_REPOSITORY}/${PACKAGE_DIR}/Caravel/Master/Linux
+MAKE_TARGETS="drod-custom"
+export DESTDIR=${PUBLISH_DIR}/.data
 
 ConfigureStep() {
   export CC=${NACLCC}
@@ -23,12 +21,6 @@ ConfigureStep() {
                      -lvorbis -logg -lfreetype -lSDLmain -ltar -lnacl_io"
 }
 
-BuildStep() {
-  ChangeDir ${NACL_PACKAGES_REPOSITORY}/${PACKAGE_DIR}/Caravel/Master/Linux
-  export MAKE_TARGETS="drod-custom"
-  DefaultBuildStep
-}
-
 InstallStep() {
   DefaultInstallStep
 
@@ -47,6 +39,3 @@ InstallStep() {
     sed -i.bak 's/x-nacl/x-pnacl/g' ${PUBLISH_DIR}/drod.html
   fi
 }
-
-PackageInstall
-exit 0