Add sethostname(2).

Not very useful, but helps building stuff like toybox out of the box.

Change-Id: I110e39030452bd093a84278e019c5752d293718d
diff --git a/libc/arch-arm64/syscalls/sethostname.S b/libc/arch-arm64/syscalls/sethostname.S
new file mode 100644
index 0000000..2dea457
--- /dev/null
+++ b/libc/arch-arm64/syscalls/sethostname.S
@@ -0,0 +1,14 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <private/bionic_asm.h>
+
+ENTRY(sethostname)
+    mov     x8, __NR_sethostname
+    svc     #0
+
+    cmn     x0, #(MAX_ERRNO + 1)
+    cneg    x0, x0, hi
+    b.hi    __set_errno_internal
+
+    ret
+END(sethostname)