[libFuzzer] Avoid fuzzer symbols being hidden.
Fixes
Patch By: Mike Hommey
extern "C" {
// Declare these symbols as weak to allow them to be optionally defined.
#define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN) \
- __attribute__((weak)) RETURN_TYPE NAME FUNC_SIG
+ __attribute__((weak, visibility("default"))) RETURN_TYPE NAME FUNC_SIG
#include "FuzzerExtFunctions.def"
