oeqa: allow customizing image used by runqemu()

runqemu() takes all parameters for the virtual machine from the
variables of the given recipe. By allowing the caller to provide a
hash with variables that get applied locally, the caller gets more
control.

Here's the intended usage:

   <prepare internal-image in self.resultdir>
   overrides = {
        'DEPLOY_DIR_IMAGE': self.resultdir,
        'IMAGE_LINK_NAME': 'internal-image-%s' % self.image_arch,
   }
   with runqemu('refkit-installer-image', ssh=False,
                 overrides=overrides) as qemu:
       ....

This can be used to replace the image completely with something else
or to copy it before allowing runqemu() to write into it.

(From OE-Core rev: 4c6ba32abd6b9de33f4b8a0b87e8a56432ed7825)

Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/utils/commands.py

@@ -225,7 +225,7 @@ def create_temp_layer(templayerdir, templayername, priority=999, recipepathspec=
 
 
 @contextlib.contextmanager
-def runqemu(pn, ssh=True, runqemuparams='', image_fstype=None, launch_cmd=None, qemuparams=None):
+def runqemu(pn, ssh=True, runqemuparams='', image_fstype=None, launch_cmd=None, qemuparams=None, overrides={}):
     """
     launch_cmd means directly run the command, don't need set rootfs or env vars.
     """
@@ -247,6 +247,8 @@ def runqemu(pn, ssh=True, runqemuparams='', image_fstype=None, launch_cmd=None,
             tinfoil.config_data.setVar("FIND_ROOTFS", '1')
 
         recipedata = tinfoil.parse_recipe(pn)
+        for key, value in overrides.items():
+            recipedata.setVar(key, value)
 
         # The QemuRunner log is saved out, but we need to ensure it is at the right
         # log level (and then ensure that since it's a child of the BitBake logger,