stage1: remove unneeded extern function

src/main.cpp

@@ -18,12 +18,6 @@
 
 #include <stdio.h>
 
-// Define this symbol here so that we can link with the zig objects during the
-// compiler bootstrap phase
-extern "C" {
-    void __zig_probe_stack(void) { }
-}
-
 static int print_error_usage(const char *arg0) {
     fprintf(stderr, "See `%s --help` for detailed usage information\n", arg0);
     return EXIT_FAILURE;