compiler: prevent reduction clause for perfect-enough outer loops #5907

Job	Run time
pytest-ubuntu-py311-gcc11-noomp-base	57m 21s
pytest-ubuntu-py311-gcc11-noomp-adjoint	1h 4m 19s
pytest-ubuntu-py38-gcc12-omp-base	56m 11s
pytest-ubuntu-py38-gcc12-omp-adjoint	47m 55s
pytest-ubuntu-py37-gcc7-omp-base	1h 0m 26s
pytest-ubuntu-py37-gcc7-omp-adjoint	1h 6m 34s
pytest-ubuntu-py310-gcc10-noomp-base	57m 22s
pytest-ubuntu-py310-gcc10-noomp-adjoint	1h 2m 57s
pytest-ubuntu-py38-gcc8-omp-base	53m 1s
pytest-ubuntu-py38-gcc8-omp-adjoint	1h 14m 0s
pytest-ubuntu-py39-gcc9-omp-base	51m 15s
pytest-ubuntu-py39-gcc9-omp-adjoint	52m 59s
pytest-osx-py37-clang-omp-base	8m 49s
pytest-docker-py39-gcc-omp-base	1h 18m 21s
pytest-docker-py39-gcc-omp-adjoint	56m 26s
pytest-docker-py39-icx-omp-base	53m 44s
pytest-docker-py39-icx-omp-adjoint	54m 17s
	15h 55m 57s

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