pathmapper: don't use temporary lists #1916

Job	Run time
No leftovers	1m 31s
build_test_container	1m 31s
CWL conformance (v1.0, docker)	1m 30s
Test on macos-latest	1m 33s
CWL conformance (v1.0, singularity)	1m 31s
cwltool release test	1m 43s
CWL conformance (v1.0, podman)	1m 31s
CWL conformance (v1.1, docker)	1m 32s
Tox (3, 8, lint)	1s
CWL conformance (v1.1, singularity)	1m 32s
Linters (lintreadme)	50s
Tox (3, 8, unit)	1s
CWL conformance (v1.1, podman)	1m 31s
Linters (shellcheck)	11s
Tox (3, 8, bandit)	1s
CWL conformance (v1.2, docker)	1m 31s
Tox (3, 8, mypy)	1s
Linters (pydocstyle)	16s
CWL conformance (v1.2, singularity)	1m 30s
Tox (3, 9, lint)	1s
CWL conformance (v1.2, podman)	1m 28s
Tox (3, 9, unit)	1s
CWL conformance (v1.2, docker, --fast-parser)	1m 30s
Tox (3, 9, bandit)	1s
Tox (3, 9, mypy)	1s
Tox (3, 10, lint)	29s
Tox (3, 10, unit)	42s
Tox (3, 10, bandit)	24s
Tox (3, 10, mypy)	42s
Tox (3, 11, lint)	26s
Tox (3, 11, unit)	1s
Tox (3, 11, bandit)	1s
Tox (3, 11, mypy)	1s
Tox (3, 12, lint)	1s
Tox (3, 12, unit)	1s
Tox (3, 12, bandit)	1s
Tox (3, 12, mypy)	1s
	25m 39s

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