Add top level build script for building packages.

ports/SDL/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
 
 AutogenStep() {
   ChangeDir ${NACL_PACKAGES_REPOSITORY}/${PACKAGE_NAME}
   # For some reason if we don't remove configure before running
   # autoconf it doesn't always get updates correctly.  About half
   # the time the old configure script (with no reference to nacl)
   # will remain after ./autogen.sh
   rm -f configure
   ./autogen.sh
   PatchConfigure
@@ skipping 18 matching lines @@
 
   local conf_host=${NACL_CROSS_PREFIX}
   if [ ${NACL_ARCH} = "pnacl" ]; then
     # The PNaCl tools use "pnacl-" as the prefix, but config.sub
     # does not know about "pnacl".  It only knows about "le32-nacl".
     # Unfortunately, most of the config.subs here are so old that
     # it doesn't know about that "le32" either.  So we just say "nacl".
     conf_host="nacl"
   fi
 
-  ChangeDir ${NACL_PACKAGES_REPOSITORY}/${PACKAGE_NAME}
-  MakeDir ${NACL_BUILD_SUBDIR}-test
-  ChangeDir ${NACL_BUILD_SUBDIR}-test
+  BUILD_DIR=${NACL_PACKAGES_REPOSITORY}/${PACKAGE_NAME}/${NACL_BUILD_SUBDIR}-test
+  ChangeDir ${BUILD_DIR}
 
   LIBS="$LDFLAGS" LogExecute ../test/configure \
     --host=${conf_host} \
     --disable-assembly \
     --disable-pthread-sem \
     --prefix=${NACLPORTS_PREFIX} \
     --exec-prefix=${NACLPORTS_PREFIX} \
     --libdir=${NACLPORTS_LIBDIR} \
     --oldincludedir=${NACLPORTS_INCLUDE}
 }
@@ skipping 62 matching lines @@
   ExtractStep
   PatchStep
   AutogenStep
   ConfigureStep
   BuildStep
   InstallStep
   ConfigureTests
   BuildStep
   PublishStep
 }
-
-
-PackageInstall
-exit 0