bpo-32217: Correct usage of ABI tags in freeze. (GH-4719)

Check for sys.abiflags before using since not all platforms have it defined.

Misc/NEWS.d/next/Tools-Demos/2017-12-19-20-42-36.bpo-32217.axXcjA.rst

+Fix freeze script on Windows.

Tools/freeze/freeze.py

@@ -217,7 +217,10 @@ def main():
 
     # locations derived from options
     version = '%d.%d' % sys.version_info[:2]
-    flagged_version = version + sys.abiflags
+    if hasattr(sys, 'abiflags'):
+        flagged_version = version + sys.abiflags
+    else:
+        flagged_version = version
     if win:
         extensions_c = 'frozen_extensions.c'
     if ishome: