conflict between Centipede's and ASAN's interceptors

[kcc]

Centipede intercepts memcmp (and will intercept more in future).
Sanitizers (ASAN, etc) also intercept the same functions.
The way we currently build binaries for Centipede's --extra_binaries= makes these interceptors conflict.

% cat memcmp_fuzz.cc 
#include <cstdint>
#include <cstddef>
#include <cstring>

volatile auto M = &memcmp;

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
  char x[3] = {'z', 'z', 'z'};
  if (size != 2) return 0;
  M(x, data, 3);  // should trigger an ASAN report.
  return 0;
}

% clang -O2 -fsanitize=address,fuzzer ./memcmp_fuzz.cc -o lf
% ./lf zz  2>&1 | grep ERROR 
==3371320==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000000032 at pc 0x56499c281f3c bp 0x7ffc82201d00 sp 0x7ffc822014b0

libFuzzer+ASAN can easily detect a buffer overflow inside memcmp.

% clang++ @$CENTIPEDE/clang-flags.txt -c memcmp_fuzz.cc 
% clang++ memcmp_fuzz.o ./bazel-bin/libcentipede_runner.pic.a -fsanitize=address -ldl -lrt -lpthread -o memcmp_centipede
% ./memcmp_centipede zz
Centipede fuzz target runner; argv[0]: ./memcmp_centipede flags: (null)
Not using RLIMIT_AS; VmSize is 20480Gb, suspecting ASAN/MSAN/TSAN
<no report>

Internally, we build Centipede's runner together with the target, and the #if !defined(ADDRESS_SANITIZER) inside runner_interceptors.cc avoids this problem.