message: Fix build type in appveyor yaml.
diff: @@ -12,7 +12,7 @@ before_build:
  - cmake . -Bbuild -G "Visual Studio 15 2017 Win64"
  build_script:
  -- cmake --build build
  +- cmake --build build --config %CMAKE_BUILD_TYPE%
  after_build:
  -- cmake --build build --target check
  +- cmake --build build --target check --config %CMAKE_BUILD_TYPE%
  