message: Move `checkout` step to jobs section for consistency
  This will become more important to the MacOS job, as the packages are
  installed (and cached) using the package list form the NAS2D repository.
  Such an organization will require the code to be checked out first so
  the package list is accessible.
diff: @@ -3,7 +3,6 @@ version: 2.1
  commands:
  build:
  steps:
  - - checkout
  - run: git submodule update --init nas2d-core/
  - run: make --keep-going --jobs 16 CXXFLAGS_EXTRA="-Werror" nas2d
  - run: make --keep-going --jobs 16 CXXFLAGS_EXTRA="-Werror"
  @@ -34,6 +33,7 @@ jobs:
  environment:
  - WARN_EXTRA: "-Wno-double-promotion"
  steps:
  + - checkout
  - brew-install:
  packages: physfs sdl2 sdl2_image sdl2_mixer sdl2_ttf libpng libjpeg libtiff webp libmodplug libvorbis libogg freetype glew googletest
  - build
  @@ -41,6 +41,7 @@ jobs:
  docker:
  - image: outpostuniverse/nas2d:1.4
  steps:
  + - checkout
  - build
  build-linux-gcc:
  docker:
  @@ -48,6 +49,7 @@ jobs:
  environment:
  WARN_EXTRA: -Wsuggest-override
  steps:
  + - checkout
  - build
  build-linux-clang:
  docker:
  @@ -55,6 +57,7 @@ jobs:
  environment:
  WARN_EXTRA: -Wimplicit-int-conversion -Wunreachable-code -Wunreachable-code-return -Wunreachable-code-break -Wextra-semi-stmt -Wnewline-eof -Wdocumentation -Wheader-hygiene -Winconsistent-missing-destructor-override -Wdeprecated-copy-dtor -Wformat-nonliteral
  steps:
  + - checkout
  - build
  build-linux-mingw:
  docker:
  