Handle missing os.sysconf more gracefully

os.sysconf is not available on all platforms (like Windows) but it
is used to retrieve the number of online processors. If missing,
assume one processor (building on such a platform will most likely
not work, though).

Fixes: #948 ("Windows compatibility") (at least it improves the
Windows support a bit)

osc/conf.py

@@ -87,11 +87,11 @@
 def _get_processors():
     """
     get number of processors (online) based on
-    SC_NPROCESSORS_ONLN (returns 1 if config name does not exist).
+    SC_NPROCESSORS_ONLN (returns 1 if config name/os.sysconf does not exist).
     """
     try:
         return os.sysconf('SC_NPROCESSORS_ONLN')
-    except ValueError as e:
+    except (AttributeError, ValueError):
         return 1