Actually use qt5.12 in CI

.gitlab-ci.yml

@@ -11,13 +11,13 @@ build-gcc7:
   variables:
     CXX: g++-7
     CC: gcc-7
-    QT_PKG: 510
+    QT_PKG: 512
     TRAVIS_OS_NAME: linux
   before_script:
     - apt-get update
     - apt-get install -y software-properties-common
     - add-apt-repository ppa:ubuntu-toolchain-r/test -y
-    - add-apt-repository ppa:beineri/opt-qt-5.10.1-xenial -y
+    - add-apt-repository ppa:beineri/opt-qt-5.12.9-xenial -y
     - apt-get update && apt-get -y install --no-install-recommends g++-7 build-essential ninja-build qt${QT_PKG}{base,declarative,tools,multimedia,script,quickcontrols2,svg} liblmdb-dev libgl1-mesa-dev libssl-dev git ccache
     # need recommended deps for wget
     - apt-get -y install wget