VCPKG adds /external:W0 which results in more warnings

Author: walbourn

build/CompilerAndLinker.cmake

@@ -136,7 +136,8 @@ elseif(CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
       list(APPEND COMPILER_SWITCHES /Zc:lambda)
     endif()
 
-    if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 19.29)
+    if((CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 19.29)
+       AND (NOT VCPKG_TOOLCHAIN))
       list(APPEND COMPILER_SWITCHES /external:W4)
     endif()