message: Update MacOS image to Xcode 12.5.0
  Bumping Xcode version from 12.4.0 to 12.5.0. This means an updated macOS
  version being bumped from 10.15.5 to 11.4.0.
  Bump cache version to force rebuild of dependencies with updated
  compiler.
diff: @@ -6,11 +6,11 @@ commands:
  steps:
  - restore_cache:
  name: Restoring brew dependencies
  - key: deps-OPHD-{{ arch }}-v1-{{ checksum "nas2d-core/BrewDeps.txt" }}
  + key: deps-OPHD-{{ arch }}-v2-{{ checksum "nas2d-core/BrewDeps.txt" }}
  - run: make --directory nas2d-core/ install-dependencies
  - save_cache:
  name: Caching brew dependencies
  - key: deps-OPHD-{{ arch }}-v1-{{ checksum "nas2d-core/BrewDeps.txt" }}
  + key: deps-OPHD-{{ arch }}-v2-{{ checksum "nas2d-core/BrewDeps.txt" }}
  paths:
  - /usr/local/Cellar
  build:
  @@ -24,7 +24,7 @@ commands:
  jobs:
  build-macos:
  macos:
  - xcode: "12.4.0"
  + xcode: "12.5.0"
  environment:
  - HOMEBREW_NO_AUTO_UPDATE: 1
  - WARN_EXTRA: "-Wno-double-promotion"
  