cmake: emscripten/clang does not support -Wformat* (anymore)

cmake/PreseedEmscriptenCache.cmake

@@ -185,8 +185,8 @@ if(EMSCRIPTEN)
     set(HAVE_GETRESUID                                   "1"   CACHE INTERNAL "Have symbol getresuid")
     set(HAVE_GETRESGID                                   "1"   CACHE INTERNAL "Have symbol getresgid")
     set(HAVE_LIBUDEV_H                                   ""    CACHE INTERNAL "Have include libudev.h")
-    set(HAVE_WFORMAT                                     "1"   CACHE INTERNAL "Test COMPILER_SUPPORTS_WFORMAT")
-    set(HAVE_WFORMAT_OVERFLOW                            "1"   CACHE INTERNAL "Test COMPILER_SUPPORTS_WFORMAT_OVERFLOW")
+    set(HAVE_WFORMAT                                     ""    CACHE INTERNAL "Test COMPILER_SUPPORTS_WFORMAT")
+    set(HAVE_WFORMAT_OVERFLOW                            ""    CACHE INTERNAL "Test COMPILER_SUPPORTS_WFORMAT_OVERFLOW")
     set(HAVE_WFORMAT_EXTRA_ARGS                          "1"   CACHE INTERNAL "Test COMPILER_SUPPORTS_WFORMAT_EXTRA_ARGS")
     set(COMPILER_SUPPORTS_FCOLOR_DIAGNOSTICS             "1"   CACHE INTERNAL "Test COMPILER_SUPPORTS_FCOLOR_DIAGNOSTICS")
   endfunction()