Here's the second half of adding a migration compatibility test to CI.

We've already added support for running the full set of migration
tests with two QEMU binaries since commit 5050ad2a380
("tests/qtest/migration: Support more than one QEMU binary"), now
what's left is adding it to the CI.

I included patches that solve the problem of testing older QEMUs with
new test code. The old QEMU might lack features, bug fixes, etc. that
the tests expect to be present. After this series we can specify a
minimal QEMU version that a specific test supports.

I have NOT solved the issue of a QEMU command line change breaking
older QEMUs because that is outside of the migration realm an we're
about to release 8.2 anyway, so let's kick that problem to the
future. Hopefully it won't happen again soon.

Let me know what you think.

CI run: https://gitlab.com/farosas/qemu/-/pipelines/1098975378

Fabiano Rosas (5):
  tests/qtest: Add a helper to query the QEMU version
  tests/qtest/migration: Add infrastructure to skip tests on older QEMUs
  tests/qtest/migration: Adapt tests to use older QEMUs
  ci: Add a migration compatibility test job
  [NOT FOR MERGE] compat hack until 8.2 is out

 .gitlab-ci.d/buildtest.yml      | 43 +++++++++++++++++++++++
 tests/qtest/libqtest.c          | 25 ++++++++++++-
 tests/qtest/libqtest.h          | 10 ++++++
 tests/qtest/migration-helpers.c | 11 ++++++
 tests/qtest/migration-helpers.h |  1 +
 tests/qtest/migration-test.c    | 62 +++++++++++++++++++++++++++++----
 6 files changed, 144 insertions(+), 8 deletions(-)

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2.35.3