musl-libc doesn't provide GNU version of strerror_r but uses BSD/XSI one (#1911)

* harness: correct include and sort

warning redirecting incorrect #include <sys/errno.h> to <errno.h>

Signed-off-by: David Heidelberg <david@ixit.cz>

test_common/harness/ThreadPool.cpp

@@ -33,9 +33,9 @@
 #include "mingw_compat.h"
 #include <process.h>
 #else // !_WIN32
+#include <errno.h>
 #include <pthread.h>
 #include <unistd.h>
-#include <sys/errno.h>
 #ifdef __linux__
 #include <sched.h>
 #endif