Reproducible nondeterministic failure in test_fortran.py:test_fuse_kernels

As of 28b164f3

Using Python 3.6 and POCL 09cf952f4eeb79825bfa8e09198cd4c6e106d0a0, I get the following:

$ PYTHONHASHSEED=1 python test_fortran.py "test_fuse_kernels(cl._csc)"
...
loopy.diagnostic.AutomaticTestFailure: results do not match -- (rel) l_2 err: 0.438444, l_inf err: 1

$ PYTHONHASHSEED=2 python test_fortran.py "test_fuse_kernels(cl._csc)"
...
elapsed: 0.000148188 s event, 0.000111179 s marker-event 0.000111193 s wall (8192 rounds)
ref: elapsed: 0.000194346 s event, 0.0121503 s wall

The effect of PYTHONHASHSEED suggests that this is due to some sort of hashing issue, possibly container ordering.

The failure is also visible here: https://gitlab.tiker.net/inducer/loopy/-/jobs/39540