Corrade: Drop vs2017 workaround when building HEAD for vs2019 (micros…

…oft#7566)

* Corrade: Make sure to drop vs2017 workaround when building HEAD for vs2019

Otherwise building HEAD is broken.

Also add a warning about current Corrade release not supporting vs2019,
suggesting to use HEAD instead.

* [corrade] this option name is wrong.

ports/corrade/portfile.cmake

@@ -26,13 +26,23 @@ foreach(_feature IN LISTS ALL_FEATURES)
     endif()
 endforeach()
 
+if(NOT VCPKG_CMAKE_SYSTEM_NAME)
+  # building for Windows desktop
+  if (VCPKG_PLATFORM_TOOLSET STREQUAL "v142" AND NOT VCPKG_USE_HEAD_VERSION)
+    message("**********")
+    message("WARNING: Visual Studio 2019 is not official supported by Corrade/Magnum team. Please use --head version if you intend to have upstream support.")
+    message("**********")
+    set(_CUSTOM_BUILD_FLAGS "-DCORRADE_MSVC2017_COMPATIBILITY=ON")
+  endif()
+endif()
+
 vcpkg_configure_cmake(
     SOURCE_PATH ${SOURCE_PATH}
     PREFER_NINJA # Disable this option if project cannot be built with Ninja
     OPTIONS
-        -DDUTILITY_USE_ANSI_COLORS=ON
+        -DUTILITY_USE_ANSI_COLORS=ON
         -DBUILD_STATIC=${BUILD_STATIC}
-        -DCORRADE_MSVC2017_COMPATIBILITY=ON
+        ${_CUSTOM_BUILD_FLAGS}
         ${_COMPONENT_FLAGS}
 )