Bug#976891: Unable to find next sigaction in signal chain

[Hans-Christoph Steiner]

Now fastboot and aapt build and link but both report this error:

   Unable to find next sigaction in signal chain

Looks like some dynamically loaded code is missing, the error is in 
sigchainlib/sigchain.cc:

static void lookup_next_symbol(T* output, T wrapper, const char* name) {
  void* sym = dlsym(RTLD_NEXT, name);  // NOLINT glibc triggers 
cert-dcl16-c with RTLD_NEXT.
  if (sym == nullptr) {
    sym = dlsym(RTLD_DEFAULT, name);
    if (sym == wrapper || sym == sigaction) {
      fatal("Unable to find next %s in signal chain", name);
    }
  }
  *output = reinterpret_cast<T>(sym);
}