qapi: add 'query-target' command to return target arch

Add a 'query-target' QAPI command to allow management applications
to determine what target architecture a QEMU binary is emulating
without having to parse the binary name or -help output

  $ qmp-shell -p /tmp/qemu
  (QEMU) query-target
  {   u'return': {   u'arch': u'x86_64' }}

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 2ce4ce6..00d798f 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -2509,3 +2509,8 @@
         .mhandler.cmd_new = qmp_marshal_input_query_cpu_definitions,
     },
 
+    {
+        .name       = "query-target",
+        .args_type  = "",
+        .mhandler.cmd_new = qmp_marshal_input_query_target,
+    },