Change the install location of _sysconfigdata.py

The _sysconfigdata.py module contains definitions that are needed when
building Python modules. In cross-compilation mode, when building
Python extensions for the target, we need to use the _sysconfigdata.py
of the target Python while executing the host Python.

However until now, the _sysconfigdata.py module was installed in
build/lib.<arch>-<version> directory, together with a number of
architecture-specific shared objects, which cannot be used with the
host Python.

To solve this problem, this patch moves _sysconfigdata.py to a
separate location, build/sysconfigdata.<arch>-<version>/, and only
this directory gets added to the PYTHONPATH of the host Python
interpreter when building Python modules for the target.

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

Index: b/Makefile.pre.in
===================================================================
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -543,6 +543,9 @@
 # sys.path fixup -- see Modules/getpath.c.
 pybuilddir.txt: $(BUILDPYTHON)
 	$(RUNSHARED) $(PYTHON_FOR_BUILD) -S -m sysconfig --generate-posix-vars
+	echo `cat pybuilddir.txt`/sysconfigdata > pysysconfigdatadir.txt
+	mkdir -p `cat pysysconfigdatadir.txt`
+	cp `cat pybuilddir.txt`/_sysconfigdata.py `cat pysysconfigdatadir.txt`
 
 # Build the shared modules
 # Under GNU make, MAKEFLAGS are sorted and normalized; the 's' for
@@ -1181,7 +1184,7 @@
 		else	true; \
 		fi; \
 	done
-	@for i in $(srcdir)/Lib/*.py `cat pybuilddir.txt`/_sysconfigdata.py; \
+	@for i in $(srcdir)/Lib/*.py ; \
 	do \
 		if test -x $$i; then \
 			$(INSTALL_SCRIPT) $$i $(DESTDIR)$(LIBDEST); \
@@ -1191,6 +1194,11 @@
 			echo $(INSTALL_DATA) $$i $(LIBDEST); \
 		fi; \
 	done
+	$(INSTALL_DATA) `cat pysysconfigdatadir.txt`/_sysconfigdata.py \
+		$(DESTDIR)$(LIBDEST)
+	mkdir -p $(DESTDIR)$(LIBDEST)/sysconfigdata
+	$(INSTALL_DATA) `cat pysysconfigdatadir.txt`/_sysconfigdata.py \
+		$(DESTDIR)$(LIBDEST)/sysconfigdata
 	@for d in $(LIBSUBDIRS); \
 	do \
 		a=$(srcdir)/Lib/$$d; \
@@ -1514,7 +1522,7 @@
 	find build -name 'fficonfig.h' -exec rm -f {} ';' || true
 	find build -name '*.py' -exec rm -f {} ';' || true
 	find build -name '*.py[co]' -exec rm -f {} ';' || true
-	-rm -f pybuilddir.txt
+	-rm -f pybuilddir.txt pysysconfigdatadir.txt
 	-rm -f Lib/lib2to3/*Grammar*.pickle
 	-rm -f Modules/_testembed Modules/_freeze_importlib
 
Index: b/configure.ac
===================================================================
--- a/configure.ac
+++ b/configure.ac
@@ -67,7 +67,7 @@
 	    AC_MSG_ERROR([python$PACKAGE_VERSION interpreter not found])
 	fi
         AC_MSG_RESULT($interp)
-	PYTHON_FOR_BUILD='_PYTHON_PROJECT_BASE=$(abs_builddir) _PYTHON_HOST_PLATFORM=$(_PYTHON_HOST_PLATFORM) PYTHONPATH=$(shell test -f pybuilddir.txt && echo $(abs_builddir)/`cat pybuilddir.txt`:)$(srcdir)/Lib:$(srcdir)/Lib/$(PLATDIR) '$interp
+	PYTHON_FOR_BUILD='_PYTHON_PROJECT_BASE=$(abs_builddir) _PYTHON_HOST_PLATFORM=$(_PYTHON_HOST_PLATFORM) PYTHONPATH=$(shell test -f pysysconfigdatadir.txt && echo $(abs_builddir)/`cat pysysconfigdatadir.txt`:)$(srcdir)/Lib:$(srcdir)/Lib/$(PLATDIR) '$interp
     fi
 elif test "$cross_compiling" = maybe; then
     AC_MSG_ERROR([Cross compiling required --host=HOST-TUPLE and --build=ARCH])