Meta: Diable Wshorten-64-to-32 explicitly to silence Xcode defaults

Xcode will set this by default when creating a new project unless we
set an xcode property to disable it. Instead of doing that, disable
it globally.

Meta/CMake/lagom_compile_options.cmake

@@ -3,6 +3,7 @@ include(${CMAKE_CURRENT_LIST_DIR}/common_compile_options.cmake)
 add_compile_options(-Wno-implicit-const-int-float-conversion)
 add_compile_options(-Wno-literal-suffix)
 add_compile_options(-Wno-maybe-uninitialized)
+add_compile_options(-Wno-shorten-64-to-32)
 add_compile_options(-Wno-unknown-warning-option)
 add_compile_options(-Wno-unused-command-line-argument)
 add_compile_options(-fsigned-char)