[PyQt] --static configure of sip tries to install sip.pyd not sip.lib

[Kyle Altendorf]

It looks like the SIP configure.py is getting an extension wrong when 
--static is specified.  It writes 'sip.pyd' to 'installed.txt' rather 
than 'sip.lib'.  This results in the install setp failing because the 
.pyd is not present.

https://ci.appveyor.com/project/KyleAltendorf/pyqt5-tools/build/464/job/9hg5x434a0du76dy#L2358

FileNotFoundError: [Errno 2] No such file or directory: 
'C:\\projects\\pyqt5-tools\\sysroot\\native\\Lib\\site-packages\\PyQt5\\sip.pyd'

Maybe:

         mod_ext = '.pyd' if sys.platform == 'win32' else '.so'

should be:

         if sys.platform == 'win32':
             mod_ext = '.lib' if opts.static else '.pyd'
         else:
             mod_ext = '.so'

I observed this directly in 4.19.12 but at least the symptom was present 
in 4.19.11.

Then again, maybe something else entirely is the issue since I really 
don't know my way around these builds.

Cheers,
-kyle