Fix compiler warnings (#3784)

The definition of os_get_invalid_handle in platform_internal.h did not
match the declaration in platform_api_extension.h.

core/shared/platform/windows/platform_internal.h

@@ -188,7 +188,7 @@ typedef uint32_t os_raw_file_handle;
 #endif
 
 static inline os_file_handle
-os_get_invalid_handle()
+os_get_invalid_handle(void)
 {
     return NULL;
 }