clean up distutils argument handling in cythonize script, avoid unnecessary...

clean up distutils argument handling in cythonize script, avoid unnecessary cwd changing, move intermediate compiler artifacts into temp directory and delete them afterwards

Cython/Build/Cythonize.py

 #!/usr/bin/env python
 
 import os
-import sys
+import shutil
+import tempfile
 
 from distutils.core import setup
 from Cython.Build.Dependencies import cythonize, extended_iglob
@@ -77,10 +78,6 @@ def cython_compile(path_pattern, options):
                 # assume it's a file(-like thing)
                 paths = [path]
 
-            cwd = os.getcwd()
-            try:
-                if base_dir:
-                    os.chdir(base_dir)
             ext_modules = cythonize(
                 paths,
                 nthreads=options.parallel,
@@ -90,9 +87,6 @@ def cython_compile(path_pattern, options):
                 force=options.force,
                 quiet=options.quiet,
                 **options.options)
-            finally:
-                if base_dir:
-                    os.chdir(cwd)
 
             if ext_modules and options.build:
                 if len(ext_modules) > 1 and options.parallel > 1:
@@ -117,15 +111,24 @@ def cython_compile(path_pattern, options):
 
 def run_distutils(args):
     base_dir, ext_modules = args
-    sys.argv[1:] = ['build_ext', '-i']
+    script_args = ['build_ext', '-i']
     cwd = os.getcwd()
+    temp_dir = None
     try:
         if base_dir:
             os.chdir(base_dir)
-        setup(ext_modules=ext_modules)
+            temp_dir = tempfile.mkdtemp(dir=base_dir)
+            script_args.extend(['--build-temp', temp_dir])
+        setup(
+            script_name='setup.py',
+            script_args=script_args,
+            ext_modules=ext_modules,
+        )
     finally:
         if base_dir:
             os.chdir(cwd)
+            if temp_dir and os.path.isdir(temp_dir):
+                shutil.rmtree(temp_dir)
 
 
 def parse_args(args):