scripts/runqemu: Add snapshot support

Allow access to the snapshot option of qemu to simplify some of our runtime testing to avoid copying images.

index a94cc65..867e818 100755
@@ -160,7 +160,8 @@ class BaseConfig(object):

         self.custombiosdir = ''
         self.lock = ''
         self.lock_descriptor = ''
-        self. bitbake_e = ''
+        self.bitbake_e = ''
+        self.snapshot = False
         self.fstypes = ('ext2', 'ext3', 'ext4', 'jffs2', 'nfs', 'btrfs', 'cpio.gz', 'cpio', 'ramfs') self.vmtypes = ('hddimg', 'hdddirect', 'wic', 'vmdk', 'qcow2', 'vdi', 'iso')
@@ -312,6 +313,8 @@ class BaseConfig(object):
                 self.vhost_enabled = True
             elif arg == 'slirp':
                 self.slirp_enabled = True
+            elif arg == 'snapshot':
+                self.snapshot = True
             elif arg == 'publicvnc':
                 self.qemu_opt_script += ' -vnc :0'
             elif arg.startswith('tcpserial='):
@@ -750,6 +753,9 @@ class BaseConfig(object):
         # Enable virtio RNG else we can run out of entropy in guests
         self.qemu_opt += " -device virtio-rng-pci"

+        if self.snapshot:
+            self.qemu_opt += " -snapshot"
+
         if self.serialstdio:
             logger.info("Interrupt character is '^]'")
             cmd = "stty intr ^]"