giscanner: unbreak g-ir-annotationtool...

giscanner: unbreak g-ir-annotationtool...

... and by extension misc/update-glib-annotations.py.

Commit 5c70ef2eb32949f8889e9ae654d50bfbf838951f broke
these by assuming create_source_scanner() is always
called with 'options' and 'args' built by the
OptionParser() defined in scannermain.py's
_get_option_parser().

This is not the case with g-ir-annotationtool, where
annotationmain.py's annotation_main() creates it's
own OptionParser() accepting a different set of
'options' and 'args' as compared to scannermain.py