Qt 5.11 was downgraded to 5.9 because of two issues:
- spawns errors like
```
qrc:/qml/SignInWaiting.qml:20:9: QML BusyIndicator: Detected anchors on an item that is managed by a layout. This is undefined behavior; use Layout.alignment instead.
qrc:/qml/SignInWaiting.qml:26:9: QML Text: Detected anchors on an item that is managed by a layout. This is undefined behavior; use Layout.alignment instead.
qrc:/qml/SignInWaiting.qml:20:9: QML BusyIndicator: Detected anchors on an item that is managed by a layout. This is undefined behavior; use Layout.alignment instead.
qrc:/qml/SignInWaiting.qml:26:9: QML Text: Detected anchors on an item that is managed by a layout. This is undefined behavior; use Layout.alignment instead.
qrc:/qml/SignInWaiting.qml:20:9: QML BusyIndicator: Detected anchors on an item that is managed by a layout. This is undefined behavior; use Layout.alignment instead.
qrc:/qml/SignInWaiting.qml:26:9: QML Text: Detected anchors on an item that is managed by a layout. This is undefined behavior; use Layout.alignment instead.
qrc:/qml/SignInWaiting.qml:20:9: QML BusyIndicator: Detected anchors on an item that is managed by a layout. This is undefined behavior; use Layout.alignment instead.
qrc:/qml/SignInWaiting.qml:26:9: QML Text: Detected anchors on an item that is managed by a layout. This is undefined behavior; use Layout.alignment instead.
qrc:/qml/SignInWaiting.qml:20:9: QML BusyIndicator: Detected anchors on an item that is managed by a layout. This is undefined behavior; use Layout.alignment instead.
qrc:/qml/SignInWaiting.qml:26:9: QML Text: Detected anchors on an item that is managed by a layout. This is undefined behavior; use Layout.alignment instead.
```
- Google login doesn't work. It just doesn't start embedded webbrowser
Build failed after update to 4.4.0 because the tests are incorrectly
packages in the pypi version.
Switch to upstream github repo, fix tests, disable failing test cases
This allows the definition of a custom derivation of Exim,
which can be used to enable custom features such as LDAP and PAM support.
The default behaviour remains unchanged (defaulting to pkgs.exim).