Reduce the number of times we build a host copy of python.

ports/python_modules/python-host/build.sh

-# Copyright (c) 2013 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.
-
-# Use the same patch here as for the destination tree.  This allows us to use
-# the same tree for both, although some care should be taken to note that our
-# DYNLOAD will be different between the two builds.
-BUILD_DIR=${WORK_DIR}/build-nacl-host
-
-ConfigureStep() {
-  MakeDir ${BUILD_DIR}
-  ChangeDir ${BUILD_DIR}
-  # Reset CFLAGS and LDFLAGS when configuring the host
-  # version of python since they hold values designed for
-  # building for NaCl.  Note that we are forcing 32 bits here so
-  # our generated modules use Py_ssize_t of the correct size.
-  export CC="gcc -m32"
-  export CXX="g++ -m32"
-  export LD="gcc -m32"
-  LogExecute \
-    ${SRC_DIR}/configure --prefix=${NACL_HOST_PYROOT}
-}
-
-InstallStep() {
-  make install
-}