Kernel/LibC/Userspace: Implement chown and set tty owner on login

libc/include/sys/syscall.h

@@ -61,6 +61,7 @@ __BEGIN_DECLS
 #define SYS_READLINKAT 60
 #define SYS_MSYNC 61
 #define SYS_PREAD 62
+#define SYS_CHOWN 63
 
 __END_DECLS
 

libc/unistd.cpp

@@ -270,6 +270,11 @@ int chdir(const char* path)
 	return syscall(SYS_SET_PWD, path);
 }
 
+int chown(const char* path, uid_t owner, gid_t group)
+{
+	return syscall(SYS_CHOWN, path, owner, group);
+}
+
 void sync(void)
 {
 	syscall(SYS_SYNC, false);