Commit 24e996d14d (package/xvisor: fix build without python interpreter)
added a dependency on host-python3 for the d2c.py script, but this script
does not use any non-standard python modules so we can instead use
BR2_PYTHON3_HOST_DEPENDENCY to only build host-python3 if the build host
does not have python3.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 7f08dc612c)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>