core/exec-invoke: use sched_setattr instead of sched_setscheduler

The kernel's sched_setattr interface allows for more control over a processes
scheduling attributes as the previously used sched_setscheduler interface.

Using sched_setattr is also the prerequisite for support of utilization
clamping (UCLAMP [1], see #26705) and allows to set sched_runtime. The latter,
sched_runtime, will probably become a relevant scheduling parameter of the
EEVDF scheduler [2, 3], and therefore will not only apply to processes
scheduled via SCHED_DEADLINE, but also for processes scheduled via
SCHED_OTHER/SCHED_BATCH (i.e., most processes).

1: https://docs.kernel.org/next/scheduler/sched-util-clamp.html
2: https://lwn.net/Articles/969062/
3: https://lwn.net/ml/linux-kernel/20240405110010.934104715@infradead.org/

src/basic/missing_syscall.h

@@ -22,6 +22,7 @@
 
 #include "macro.h"
 #include "missing_keyctl.h"
+#include "missing_sched.h"
 #include "missing_stat.h"
 #include "missing_syscall_def.h"
 
@@ -667,6 +668,22 @@ static inline ssize_t missing_getdents64(int fd, void *buffer, size_t length) {
 
 /* ======================================================================= */
 
+#if !HAVE_SCHED_SETATTR
+
+static inline ssize_t missing_sched_setattr(pid_t pid, struct sched_attr *attr, unsigned int flags) {
+#  if defined __NR_sched_setattr
+        return syscall(__NR_sched_setattr, pid, attr, flags);
+#  else
+        errno = ENOSYS;
+        return -1;
+#  endif
+}
+
+#  define sched_setattr missing_sched_setattr
+#endif
+
+/* ======================================================================= */
+
 /* glibc does not provide clone() on ia64, only clone2(). Not only that, but it also doesn't provide a
  * prototype, only the symbol in the shared library (it provides a prototype for clone(), but not the
  * symbol in the shared library). */