acpi-build: disable with -no-acpi

QEMU will currently crash if started with -no-acpi flag
since acpi build code probes the PM device which isn't present
in this configuration.

To fix, don't expose ACPI tables to guest when acpi has been
disabled from command line.

Fixes LP# 1248854
https://bugs.launchpad.net/qemu/+bug/1248854

Reported-by: chao zhou <chao.zhou@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>

hw/i386/acpi-build.c

@@ -1182,6 +1182,11 @@ void acpi_setup(PcGuestInfo *guest_info)
         return;
     }
 
+    if (!acpi_enabled) {
+        ACPI_BUILD_DPRINTF(3, "ACPI disabled. Bailing out.\n");
+        return;
+    }
+
     build_state = g_malloc0(sizeof *build_state);
 
     build_state->guest_info = guest_info;