Switch docker to Qt 5.15

deploy/docker/Dockerfile-build-linux

@@ -5,7 +5,7 @@
 FROM ubuntu:20.04
 LABEL authors="Daniel Agar <daniel@agar.ca>, Patrick José Pereira <patrickelectric@gmail.com>"
 
-ARG QT_VERSION=5.12.10
+ARG QT_VERSION=5.15.2
 
 ENV DEBIAN_FRONTEND noninteractive
 

deploy/docker/install-qt-linux.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 
 # Set default variables
-QT_VERSION="${QT_VERSION:-5.12.10}"
+QT_VERSION="${QT_VERSION:-5.15.2}"
 QT_PATH="${QT_PATH:-/opt/Qt}"
 QT_HOST="${QT_HOST:-linux}"
 QT_TARGET="${QT_TARGET:-desktop}"