message: Add sleep to profiling
  Summary:
  Sleep a little bit after fork to let the spawn catch up.
  This improves the ability to profile short passes.
diff: #include <sys/wait.h>
  #include <unistd.h>
  #endif
  +#include <chrono>
  #include <cstdlib>
  #include <cstring>
  #include <iostream>
  #include <sstream>
  +#include <thread>
  #include "Debug.h"
  namespace {
  +using namespace std::chrono_literals;
  +
  pid_t spawn(const std::string& cmd) {
  #ifdef _POSIX_VERSION
  auto child = fork();
  always_assert_log(child != -1, "Failed to fork");
  if (child != 0) {
  + // Wait a little bit to let the spawn catch up.
  + std::this_thread::sleep_for(250ms);
  return child;
  } else {
  int ret = execl("/bin/sh", "/bin/sh", "-c", cmd.c_str(), nullptr);
  