Add dedicated image for CircleCI builds

This essentially just bakes in all the dependencies and other third
party tools that we need, preventing them from being downloaded on every
new CI run.

TravisCI does not have non-enterprise support for custom images without
a lot of hassle.

.circleci/config.yml

@@ -13,65 +13,9 @@ jobs:
             QT_SELECT: opt-qt512
             MAKE_JOBS: 2
         docker:
-            - image: circleci/buildpack-deps:xenial
+            - image: username223/ovras-appimage-build
         steps:
             - checkout
-            - run: sudo apt-get update && sudo apt-get upgrade -y
-            - run:
-                name: Get apt-key
-                # Required for LLVM
-                command: |
-                    sudo apt-get install software-properties-common apt-transport-https -y
-            - run:
-                name: Get LLVM repos
-                command: |
-                    wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
-                    sudo add-apt-repository 'deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-8 main'
-                    sudo add-apt-repository 'deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-7 main'
-                    sudo apt-get update -qq
-            - run:
-                name: Install LLVM-8 binaries
-                # clang is required due to a check by Qmake.
-                # clang-tidy-8 has new errors compared to clang-tidy-7, so we haven't upgraded.
-                command: |
-                    sudo apt-get install clang-format-8 -y
-                    sudo apt-get install clang-tidy-7 -y
-                    sudo apt-get install clang-8 -y
-                    sudo apt-get install clang -y
-            - run:
-                name: Run clang-format
-                command: python ./build_scripts/run-clang-format.py ./src -r --color always --clang-format-executable clang-format-8
-            - run:
-                name: Install g++
-                command: |
-                    sudo add-apt-repository ppa:ubuntu-toolchain-r/test
-                    sudo apt-get update
-                    sudo apt-get install g++-7 -y
-            - run:
-                name: Add required QT repos
-                command: |
-                    sudo add-apt-repository ppa:beineri/opt-qt-5.12.2-xenial -y
-                    sudo apt-get update -qq
-            - run: sudo apt-get install build-essential libgl1-mesa-dev -y
-            - run:
-                name: Install QT packages
-                command: |
-                    sudo apt-get install qt512-meta-minimal qt512multimedia qt512declarative qt512quickcontrols2 qt512quickcontrols qt512tools qt512imageformats qt512svg qt512base qtchooser -y
-            - run:
-                name: Install X11 packages
-                command: sudo apt-get install libx11-dev libxt-dev libxtst-dev -y
-            - run:
-                name: Install pulse packages
-                command: sudo apt-get install libpulse-dev -y
-            - run:
-                name: Install bear/clang-tidy
-                command: sudo apt-get install bear clang-tidy -y
-            - run:
-                name: Install SDL libs
-                command: sudo apt-get install libsdl2-2.0-0 -y
-            - run:
-                name: Set up qtchooser
-                command: qtchooser -install opt-qt512 /opt/qt512/bin/qmake
             - run:
                 name: Give build scripts +x
                 command: |
@@ -79,6 +23,9 @@ jobs:
                     chmod +x ./build_scripts/linux/format.sh
                     chmod +x ./build_scripts/linux/run-clang-tidy.sh
                     chmod +x ./build_scripts/linux/verify_formatting.sh
+            - run:
+                name: Run clang-format
+                command: python ./build_scripts/run-clang-format.py ./src -r --color always --clang-format-executable clang-format-8
             - run:
                 name: Update version number
                 command: |