Add a rule to fetch acceptance test assets.

This is particularly useful in a CI context, when a single job
can fetch and save the cache so other jobs reuse it directly.

It is also useful to measure the time spent downloading the
assets versus the time spent running the tests.

For now we have to exclude the 'boot_linux.py' which triggers
an exception.

Philippe Mathieu-Daudé (2):
  tests: Add 'fetch-acceptance' rule
  tests: Exclude 'boot_linux.py' from fetch-acceptance rule

 tests/Makefile.include | 9 +++++++++
 1 file changed, 9 insertions(+)

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2.21.3