Fix an issue that MSVC 2019 cannot compile with CMake

Fix using PCH with MSVC too, which notably fixes using it with vcpkg.

Closes https://github.com/wxWidgets/wxWidgets/pull/2372

Co-Authored-By: Maarten Bent <MaartenBent@users.noreply.github.com>

build/cmake/functions.cmake

@@ -383,7 +383,7 @@ endmacro()
 # Enable cotire for target, use optional second argument for prec. header
 macro(wx_target_enable_precomp target_name)
     target_compile_definitions(${target_name} PRIVATE WX_PRECOMP)
-    if(NOT ${ARGV1} STREQUAL "")
+    if(${ARGC} GREATER 1 AND NOT ${ARGV1} STREQUAL "")
         set_target_properties(${target_name} PROPERTIES
             COTIRE_CXX_PREFIX_HEADER_INIT ${ARGV1})
     endif()