Extensions should be installed to the targets libdir. This is important if e.g. host
has a 64bit /usr/lib64, but the target is 32bit and has $ROOT/usr/lib. Make sure we
respect the target's lib structure by getting the libdir name from Makefile.

--- a/Lib/distutils/command/build_ext.py
+++ b/Lib/distutils/command/build_ext.py
@@ -234,7 +234,8 @@ class build_ext(Command):
         if (sysconfig.get_config_var('Py_ENABLE_SHARED')):
             if not sysconfig.python_build:
                 # building third party extensions
-                self.library_dirs.append(sysconfig.get_config_var('LIBDIR'))
+                sysroot = os.getenv('SYSROOT', '')
+                self.library_dirs.append(sysroot + sysconfig.get_config_var('LIBDIR'))
             else:
                 # building python standard extensions
                 self.library_dirs.append('.')
--- a/Lib/distutils/command/install.py
+++ b/Lib/distutils/command/install.py
@@ -312,6 +312,8 @@ class install(Command):
         # everything else.
         self.config_vars['base'] = self.install_base
         self.config_vars['platbase'] = self.install_platbase
+        if not self.user and self.home is None:
+            self.config_vars['libdirname'] = self.install_libdirname
 
         if DEBUG:
             from pprint import pprint
@@ -427,6 +429,10 @@ class install(Command):
 
             self.install_base = self.prefix
             self.install_platbase = self.exec_prefix
+            self.install_libdirname = os.path.basename(get_config_vars('LIBDIR')[0])
+            if self.install_libdirname is None:
+                self.install_libdirname = '@@GENTOO_LIBDIR@@'
+
             self.select_scheme("unix_prefix")
 
     def finalize_other(self):
--- a/Lib/distutils/sysconfig.py
+++ b/Lib/distutils/sysconfig.py
@@ -10,6 +10,8 @@ Email:        <fdrake@acm.org>
 """
 
 import _imp
+import glob
+import imp
 import os
 import re
 import sys
@@ -18,11 +20,20 @@ from .errors import DistutilsPlatformError
 from .util import get_platform, get_host_platform
 
 # These are needed in a couple of spots, so just compute them once.
+SYSROOT = os.getenv('SYSROOT', '')
 PREFIX = os.path.normpath(sys.prefix)
 EXEC_PREFIX = os.path.normpath(sys.exec_prefix)
 BASE_PREFIX = os.path.normpath(sys.base_prefix)
 BASE_EXEC_PREFIX = os.path.normpath(sys.base_exec_prefix)
 
+# Make sure we respect the user specified SYSROOT environment variable.
+# This is the first step to get distutils to crosscompile stuff.
+if SYSROOT:
+    PREFIX = os.path.normpath(SYSROOT + os.path.sep + PREFIX)
+    EXEC_PREFIX = os.path.normpath(SYSROOT + os.path.sep + EXEC_PREFIX)
+    BASE_PREFIX = os.path.normpath(SYSROOT + os.path.sep + BASE_PREFIX)
+    BASE_EXEC_PREFIX = os.path.normpath(SYSROOT + os.path.sep + BASE_EXEC_PREFIX)
+
 # Path to the base directory of the project. On Windows the binary may
 # live in project/PCbuild/win32 or project/PCbuild/amd64.
 # set for cross builds
@@ -455,6 +466,11 @@ def _init_posix():
     ))
     _temp = __import__(name, globals(), locals(), ['build_time_vars'], 0)
     build_time_vars = _temp.build_time_vars
+    lib_dir = get_python_lib(plat_specific=1, standard_lib=1)
+    sysconfig_path = glob.glob(os.path.join(lib_dir, '_sysconfigdata_*.py'))
+    if sysconfig_path:
+        sysconfig_module = imp.load_source('_sysconfigdata', sysconfig_path[0])
+        build_time_vars = sysconfig_module.build_time_vars
     global _config_vars
     _config_vars = {}
     _config_vars.update(build_time_vars)