[flang][tests] add test for llvm-project#156753

[akuhlens]

This test checks that child list IO can read past the end of a record as implemented by: llvm/llvm-project#156753.

[akuhlens]

@tarunprabhu I just noticed that the reference output doesn't seem to be checked. How do I modify this PR to check the output of the program run?

[tarunprabhu]

I just built this and the test fails. It looks like the reference output is being checked, but perhaps there is something else going on.

$ llvm-lit -v Fortran/UnitTests/defined_io/llvm-project-issue-154979.test

/llvm-test-suite/tools/fpcmp-target: Compared: 1.000000e+01 and 1.200000e+01
abs. diff = 2.000000e+00 rel.diff = 1.666667e-01
Out of tolerance: rel/abs: 1.000000e-03/0.000000e+00

[akuhlens]

I just built this and the test fails. It looks like the reference output is being checked, but perhaps there is something else going on.

I just realized there was an option in my build script that was preventing the tests from running: -DTEST_SUITE_RUN_BENCHMARKS=OFF

This test won't pass until the PR in the description is landed, but I can confirm it passes now.

[akuhlens]

It is kinda wild that we don't run the Fortran test suite as a land time CI job when modifying it.