tools: enable QEMU for ARM builds

Build qemu-xen on ARM and ARM64: it is used to provide the PV backends,
disk and framebuffer in particular.

Ideally we would also modify the configure options to only build what is
necessary: a machine just for PV backends. However that is a work in
progress and not yet available in QEMU (see
http://marc.info/?l=qemu-devel&m=139082425718379&w=2). So we just build
the usual i386 target, even though no i386 emulation is going to be done
by qemu-xen on ARM.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

tools/configure

@@ -4045,6 +4045,8 @@ else
     case "$host_cpu" in
         i[3456]86|x86_64)
            qemu_xen=y;;
+        arm*|aarch64)
+           qemu_xen=y;;
         *) qemu_xen=n;;
     esac
 

tools/configure.ac

@@ -150,6 +150,8 @@ AC_ARG_WITH([system-qemu],
     case "$host_cpu" in
         i[[3456]]86|x86_64)
            qemu_xen=y;;
+        arm*|aarch64)
+           qemu_xen=y;;
         *) qemu_xen=n;;
     esac
 ])