LibC: Add POSIX timer constants

Author: https://github.com/gmta
Commit: 496988de47
Pull-request: https://github.com/SerenityOS/serenity/pull/7757

Kernel/Syscalls/sysconf.cpp

@@ -14,6 +14,8 @@ namespace Kernel {
 KResultOr<long> Process::sys$sysconf(int name)
 {
     switch (name) {
+    case _SC_MONOTONIC_CLOCK:
+        return 1;
     case _SC_NPROCESSORS_CONF:
     case _SC_NPROCESSORS_ONLN:
         return Processor::processor_count();