Add {get,set}domainname(2)

{get,set}domainname aren't in POSIX but are widely-implemented
extensions.

The Linux kernel provides a setdomainname syscall but not a symmetric
getdomainname syscall, since it expects userspace to get the domain name
from uname(2).

Change-Id: I96726c242f4bb646c130b361688328b0b97269a0
Signed-off-by: Greg Hackmann <ghackmann@google.com>
diff --git a/libc/arch-x86_64/syscalls/setdomainname.S b/libc/arch-x86_64/syscalls/setdomainname.S
new file mode 100644
index 0000000..40d1a33
--- /dev/null
+++ b/libc/arch-x86_64/syscalls/setdomainname.S
@@ -0,0 +1,15 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <private/bionic_asm.h>
+
+ENTRY(setdomainname)
+    movl    $__NR_setdomainname, %eax
+    syscall
+    cmpq    $-MAX_ERRNO, %rax
+    jb      1f
+    negl    %eax
+    movl    %eax, %edi
+    call    __set_errno_internal
+1:
+    ret
+END(setdomainname)