Add syncfs(2).

GMM calls this system call directly at the moment. That's silly.

Bug: http://b/36405699
Test: ran tests
Change-Id: I1e14c0e5ce0bc2aa888d884845ac30dc20f13cd5
diff --git a/libc/arch-arm64/syscalls/syncfs.S b/libc/arch-arm64/syscalls/syncfs.S
new file mode 100644
index 0000000..773c0cb
--- /dev/null
+++ b/libc/arch-arm64/syscalls/syncfs.S
@@ -0,0 +1,14 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <private/bionic_asm.h>
+
+ENTRY(syncfs)
+    mov     x8, __NR_syncfs
+    svc     #0
+
+    cmn     x0, #(MAX_ERRNO + 1)
+    cneg    x0, x0, hi
+    b.hi    __set_errno_internal
+
+    ret
+END(syncfs)