libc: add timerfd calls

(cherry-pick of 04c0ac14a49e0969333008a9522b64046d58fbdc.)

Change-Id: I06d0b6c2a8781602362b81f48faf1cca76b9ec05
diff --git a/libc/arch-x86/syscalls.mk b/libc/arch-x86/syscalls.mk
index b4ad564..31eb930 100644
--- a/libc/arch-x86/syscalls.mk
+++ b/libc/arch-x86/syscalls.mk
@@ -148,6 +148,9 @@
 syscall_src += arch-x86/syscalls/__timer_delete.S
 syscall_src += arch-x86/syscalls/utimes.S
 syscall_src += arch-x86/syscalls/utimensat.S
+syscall_src += arch-x86/syscalls/timerfd_create.S
+syscall_src += arch-x86/syscalls/timerfd_settime.S
+syscall_src += arch-x86/syscalls/timerfd_gettime.S
 syscall_src += arch-x86/syscalls/sigaction.S
 syscall_src += arch-x86/syscalls/sigprocmask.S
 syscall_src += arch-x86/syscalls/__sigsuspend.S