[thread_pool] topology: Use sched_getaffinity on Android

Previously, this was done with syscall(__NR_sched_getaffinity, ...) which
doesn't get the return value right.  (I saw 8 (num cpus) instead of 0.)

There doesn't seem to be a reason to use syscall(), so treat Android like
generic Linux.

PiperOrigin-RevId: 730373336

hwy/contrib/thread_pool/topology.cc

@@ -261,24 +261,20 @@ using CpuSet = cpuset_t;
 // Helper functions reduce the number of #if in GetThreadAffinity.
 int GetAffinity(CpuSet* set) {
   // To specify the current thread, pass 0 on Linux/Android and -1 on FreeBSD.
-#ifdef __ANDROID__
-  return syscall(__NR_sched_getaffinity, 0, sizeof(CpuSet), set);
-#elif HWY_OS_FREEBSD
+#if HWY_OS_FREEBSD
   return cpuset_getaffinity(CPU_LEVEL_WHICH, CPU_WHICH_TID, -1, sizeof(CpuSet),
                             set);
-#else  // normal Linux
+#else  // Linux
   return sched_getaffinity(0, sizeof(CpuSet), set);
 #endif
 }
 
 int SetAffinity(CpuSet* set) {
   // To specify the current thread, pass 0 on Linux/Android and -1 on FreeBSD.
-#ifdef __ANDROID__
-  return syscall(__NR_sched_setaffinity, 0, sizeof(CpuSet), set);
-#elif HWY_OS_FREEBSD
+#if HWY_OS_FREEBSD
   return cpuset_setaffinity(CPU_LEVEL_WHICH, CPU_WHICH_TID, -1, sizeof(CpuSet),
                             set);
-#else  // normal Linux
+#else  // Linux
   return sched_setaffinity(0, sizeof(CpuSet), set);
 #endif
 }