message: appveyor: actually compile for release
  It turns out when compiling with Visual Studio this means it is cmake
  "multi-configuration" and therefore we need to use `--config Debug`
  instead of `-DCMAKE_BUILD_TYPE="Debug"`.
diff: @@ -50,14 +50,22 @@ build_script:
  - md build
  - cd build
  - if "%configuration%"=="Debug" (
  - cmake -DWIN_CURL_INCLUDE_DIR:STRING="C:\curl-7.55.1\include" -DWIN_CURL_LIB:STRING="C:\curl-7.55.1\builds\libcurl-vc14-x64-debug-static-ipv6-sspi-winssl\lib\libcurl_a_debug.lib" -G "Visual Studio 14 2015 Win64" -DCMAKE_BUILD_TYPE="Debug" ..
  + cmake -DWIN_CURL_INCLUDE_DIR:STRING="C:\curl-7.55.1\include" -DWIN_CURL_LIB:STRING="C:\curl-7.55.1\builds\libcurl-vc14-x64-debug-static-ipv6-sspi-winssl\lib\libcurl_a_debug.lib" -G "Visual Studio 14 2015 Win64" ..
  ) else (
  - cmake -DWIN_CURL_INCLUDE_DIR:STRING="C:\curl-7.55.1\include" -DWIN_CURL_LIB:STRING="C:\curl-7.55.1\builds\libcurl-vc14-x64-release-static-ipv6-sspi-winssl\lib\libcurl_a.lib" -G "Visual Studio 14 2015 Win64" -DCMAKE_BUILD_TYPE="Release" ..
  + cmake -DWIN_CURL_INCLUDE_DIR:STRING="C:\curl-7.55.1\include" -DWIN_CURL_LIB:STRING="C:\curl-7.55.1\builds\libcurl-vc14-x64-release-static-ipv6-sspi-winssl\lib\libcurl_a.lib" -G "Visual Studio 14 2015 Win64" ..
  + )
  + - if "%configuration%"=="Debug" (
  + cmake --build . --target install --config Debug
  + ) else (
  + cmake --build . --target install --config Release
  )
  - - cmake --build . --target install
  test: on
  test_script:
  - cd C:\dronecore
  - - build\Debug\unit_tests_runner.exe
  + - if "%configuration%"=="Debug" (
  + build\Debug\unit_tests_runner.exe
  + ) else (
  + build\Release\unit_tests_runner.exe
  + )
  