Merge #19194: util: Don't reference errno when pthread fails.

cb38b06 util: Don't reference errno when pthread fails. (MIZUTA Takeshi)

Pull request description:

  Pthread library does not set errno.
  Pthread library's errno is returned by return value.

ACKs for top commit:
  practicalswift:
    ACK cb38b06 -- patch looks correct
  MarcoFalke:
    review ACK cb38b06
  hebasto:
    ACK cb38b06, only squashed commits since the [previous](bitcoin/bitcoin#19194 (review)) review.

Tree-SHA512: e6c950e30726e5031db97a7b84c8a9215da5ad3e5d233bcc349f812ad15957ddfe378e26d18339b9e0a5dcac2f50b47a687b87a6a6beaf6139df84f31531321e

Author: fanquake

src/util/system.cpp

@@ -1163,8 +1163,9 @@ void ScheduleBatchPriority()
 {
 #ifdef SCHED_BATCH
     const static sched_param param{};
-    if (pthread_setschedparam(pthread_self(), SCHED_BATCH, &param) != 0) {
-        LogPrintf("Failed to pthread_setschedparam: %s\n", strerror(errno));
+    const int rc = pthread_setschedparam(pthread_self(), SCHED_BATCH, &param);
+    if (rc != 0) {
+        LogPrintf("Failed to pthread_setschedparam: %s\n", strerror(rc));
     }
 #endif
 }