Avoid opening the file twice

setup.py

@@ -40,7 +40,7 @@ def has_flag(compiler, flagname):
     """
     import tempfile
     import os
-    with tempfile.NamedTemporaryFile('w', suffix='.cpp') as f:
+    with tempfile.NamedTemporaryFile('w', suffix='.cpp', delete=False) as f:
         f.write('int main (int argc, char **argv) { return 0; }')
         fname = f.name
     try: