LibC: Add sched_yield(), needed for GCC 8.3.0 build.

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/f9d3abf5d04

LibC/Makefile

@@ -43,7 +43,8 @@ LIBC_OBJS = \
        poll.o \
        locale.o \
        arpa/inet.o \
-       netdb.o
+       netdb.o \
+       sched.o
 
 ASM_OBJS = setjmp.no crti.ao crtn.ao
 

LibC/sched.cpp

@@ -0,0 +1,14 @@
+#include <sched.h>
+#include <errno.h>
+#include <Kernel/Syscall.h>
+
+extern "C" {
+
+int sched_yield()
+{
+    int rc = syscall(SC_yield);
+    __RETURN_WITH_ERRNO(rc, rc, -1);
+}
+
+}
+

LibC/sched.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+int sched_yield();
+
+__END_DECLS