qemu: enable guest_agent no matter whether softmmu is enabled

Fixes: openwrt/packages#11067

Reported-by: Rosen Penev <rosenp@gmail.com>
Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

utils/qemu/patches/0003-configure-enable-guest_agent-no-matter-whether-softm.patch

@@ -0,0 +1,27 @@
+From 296215421441b73bc6eb487f1d4e7e15e0510a77 Mon Sep 17 00:00:00 2001
+From: Yousong Zhou <yszhou4tech@gmail.com>
+Date: Fri, 7 Feb 2020 03:02:44 +0800
+Subject: [PATCH 3/5] configure: enable guest_agent no matter whether softmmu
+ is enabled
+
+guest_agent as a tool to be run on guest machines does not depend on
+whether there is a softmmu is to be built at this configure/make run
+
+Fixes a512590 ("configure: qemu-ga is only needed with softmmu targets")
+---
+ configure | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/configure b/configure
+index efe06f3c2b..552d16ca8f 100755
+--- a/configure
++++ b/configure
+@@ -6246,7 +6246,7 @@ fi
+ # Probe for guest agent support/options
+ 
+ if [ "$guest_agent" != "no" ]; then
+-  if [ "$softmmu" = no -a "$want_tools" = no ] ; then
++  if [ "$guest_agent" = "" -a "$want_tools" = no ] ; then
+       guest_agent=no
+   elif [ "$linux" = "yes" -o "$bsd" = "yes" -o "$solaris" = "yes" -o "$mingw32" = "yes" ] ; then
+       tools="qemu-ga\$(EXESUF) $tools"