mozjs: fix lib soname issue

polkit failed to build do to missing mozjs libs. The libs created are:
libmozjs-..a   libmozjs-..so

this was caused by a perl script error
Can't use 'defined(@array)' (Maybe you should just omit the defined()?) at config/milestone.pl line 58.

this script is use to determine the major and minor lib versions. I believe this
issue is do to the recent perl update.

this fixes the lib creation error and polkit build error.

I am not a perl person so this may not be the idea fix.

Signed-off-by: Armin Kuster <akuster808@gmail.com>
Acked-By: Andreas Müller <schnitzeltony@googlemail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>