Manually set CMAKE_CROSSCOMPILING on MSVC.

(cherry picked from commit accb0ddcd1)

Co-authored-by: Mark Roszko <mark.roszko@gmail.com>

cmake/ConfigurePlatform.cmake

@@ -38,6 +38,10 @@ if( MSVC )
     else()
         message(FATAL_ERROR "Failed to determine the host architecture: ${CMAKE_SYSTEM_PROCESSOR}")
     endif()
+
+    if( NOT KICAD_BUILD_ARCH STREQUAL KICAD_HOST_ARCH )
+        set( CMAKE_CROSSCOMPILING TRUE )
+    endif()
 else()
     if ( NOT CMAKE_SIZEOF_VOID_P EQUAL 8 )
         set( KICAD_BUILD_ARCH "x86" )