Make some frameworks optional so okular can be built on Android

Summary:
Disables KWallet integration if there's no KWallet, KJS if there's no
KJS and KDocTools.
Here's a list of frameworks that don't work on Android:
https://cgit.kde.org/sysadmin/ci-tooling.git/tree/local-metadata/project-ignore-rules.yaml

Test Plan: Still works locally, ran Okular and Okular Mobile on Android.

Reviewers: #okular, aacid

Subscribers: aacid

Tags: #okular

Differential Revision: https://phabricator.kde.org/D12177