Make sure setup.py reads the correct CONFIG_ARGS

The setup.py script that builds and installs all the Python modules
shipped with the interpreter looks at the CONFIG_ARGS variable stored
in the "sysconfig" module to look at the ./configure options and
adjust its behaviour accordingly.

Unfortunately, when cross-compiling, the value of CONFIG_ARGS returned
by the sysconfig are the one passed to the ./configure script of the
*host* Python and not the one we're currently building for the target.

In order to avoid that, we re-initialize the values in the sysconfig
module by re-reading the environment at the beginning of the setup.py
script, and we make sure that the CONFIG_ARGS variable is actually
part of the environment of setup.py.

See the beginning of
http://article.gmane.org/gmane.comp.python.devel/99772 for the
inspiration.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

---
 Makefile.pre.in |    4 +++-
 setup.py        |    3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)

Index: Python-3.3.0/setup.py
===================================================================
--- Python-3.3.0.orig/setup.py
+++ Python-3.3.0/setup.py
@@ -30,6 +30,9 @@
 # Were we compiled --with-pydebug or with #define Py_DEBUG?
 COMPILED_WITH_PYDEBUG = ('--with-pydebug' in sysconfig.get_config_var("CONFIG_ARGS"))
 
+sysconfig.get_config_vars()
+sysconfig._CONFIG_VARS.update(os.environ)
+
 # This global variable is used to hold the list of modules to be disabled.
 disabled_module_list = []
 
Index: Python-3.3.0/Makefile.pre.in
===================================================================
--- Python-3.3.0.orig/Makefile.pre.in
+++ Python-3.3.0/Makefile.pre.in
@@ -478,6 +478,7 @@
 sharedmods: $(BUILDPYTHON) pybuilddir.txt
 	case $$MAKEFLAGS in *s*) quiet=-q; esac; \
 	$(RUNSHARED) CC='$(CC)' LDSHARED='$(BLDSHARED)' OPT='$(OPT)' \
+		CONFIG_ARGS="$(CONFIG_ARGS)" \
 		$(PYTHON_FOR_BUILD) $(srcdir)/setup.py $$quiet build
 
 # Build static library
@@ -1183,7 +1184,8 @@
 # Install the dynamically loadable modules
 # This goes into $(exec_prefix)
 sharedinstall: sharedmods
-	$(RUNSHARED) $(PYTHON_FOR_BUILD) $(srcdir)/setup.py install \
+	$(RUNSHARED) CONFIG_ARGS="$(CONFIG_ARGS)" \
+		$(PYTHON_FOR_BUILD) $(srcdir)/setup.py install \
 	   	--prefix=$(prefix) \
 		--install-scripts=$(BINDIR) \
 		--install-platlib=$(DESTSHARED) \