Drop QtWebKit from build dependencies

[SamuAlfageme]

After having #5668 implemented and https://marketplace.owncloud.com/apps/oauth2 gaining more and more adoption, we're in the right track (platform-wise) to drop the requirement of shipping a full-blown browser together with the client.

Today I was looking at the differences and benefits we'll get in the e.g. .app bundles on install time and QtWebKit bloats the size in disk more than 50% (45.7 MB build with -DNO_SHIBBOLETH=1 vs. 92.2 MB wo/ the build flag).

[jnweiger]

Will master build without QtWebKit now?

[guruz]

@jnweiger only if you pass -DNO_SHIBBOLETH=1

[ogoffart]

The packages just need to update the package to remove this dependences.

[guruz]

I'll check macOS and NSIS now

[guruz]

NSIS and macOS merged #7158
MSI and Linux/Drone pending.
Linux OBS won't do.

[guruz]

MSI is done

[guruz]

@dschmidt @jnweiger How is this with the Linux/Drone builds? Done already so we can close here?

[jnweiger]

2.6.0 will still be done with the openSUSE Build service. I'll remove the dependency and see what happens.

[jnweiger]

https://build.opensuse.org/package/show/isv:ownCloud:desktop:daily:2.6/owncloud-client
is doing a rebuild without qtwebkit.

[jnweiger]

https://gitea.owncloud.services/client/build-linux/commit/32e709e29dd9d136067575c524bbb86ed9791516

https://gitea.owncloud.services/ownbrander/scripting/commit/a55cf01cce3f9c1de098cfded23177d081790050

done.

Tested ownCloud version 2.6.0daily20190604 (build 914) on Linux Mint 19

login with web token and password works. syncs fine. No more ocqt*qebkit packages on my system!