message: use rdtscp to retrieve processor id
diff: #include <stdio.h>
  #include <dlfcn.h>
  #include <stdint.h>
  -#include <sched.h>
  +
  +int pcm_getcpu()
  +{
  + int id = -1;
  + asm volatile (
  + "rdtscp\n\t"
  + "mov %%ecx, %0\n\t":
  + "=r" (id) :: "%rax", "%rcx", "%rdx");
  + // processor ID is in ECX: https://www.felixcloutier.com/x86/rdtscp
  + return id;
  +}
  struct {
  int (*pcm_c_build_core_event)(uint8_t id, const char * argv);
  @@ -57,7 +67,7 @@ int main(int argc, const char *argv[])
  c[i%100] = 4 * a[i%100] + b[i%100];
  PCM.pcm_c_stop();
  - lcore_id = sched_getcpu();
  + lcore_id = pcm_getcpu();
  printf("C:%lu I:%lu, IPC:%3.2f\n",
  PCM.pcm_c_get_cycles(lcore_id),
  PCM.pcm_c_get_instr(lcore_id),
  