test: ignore -Walloc-size-larger-than error for calloc() returns ENOMEM

test: ignore -Walloc-size-larger-than error for calloc() returns ENOMEM

Compiler report:

    /home/runner/work/libevent/libevent/test/regress_util.c: In function ‘test_event_calloc’:
    /home/runner/work/libevent/libevent/test/regress_util.c:1318:4: error: argument 2 value ‘9223372036854775815’ exceeds maximum object size 9223372036854775807 [-Werror=alloc-size-larger-than=]
      p = mm_calloc(EV_SIZE_MAX/2, EV_SIZE_MAX/2 + 8);
    In file included from /home/runner/work/libevent/libevent/test/../util-internal.h:37:0,
                     from /home/runner/work/libevent/libevent/test/regress_util.c:30:
    /usr/include/stdlib.h:541:14: note: in a call to allocation function ‘calloc’ declared here
     extern void *calloc (size_t __nmemb, size_t __size)

v2: clang on CI does not have this option