Patch for xrootd with derived variables #5008

Job	Run time
git_checks	8s
format	30s
linux_el8 (el8, icc, mpich)	23m 44s
linux_el8 (el8, oneapi, mpich)	22m 5s
macos (macos-11, shared)	28m 53s
CodeQL (cpp)	23m 10s
macos (macos-12, static)	4m 2s
linux_ubuntu (ubuntu20.04, gcc8, shared, mpich)	13m 49s
macos (macos-12, shared)	6m 21s
linux_ubuntu (ubuntu20.04, gcc9, shared, mpich)	17m 3s
windows (win2019, shared, serial)	12m 0s
linux_ubuntu (ubuntu20.04, gcc10, shared, mpich)	16m 28s
windows (win2019, shared, ompi)	17m 19s
linux_ubuntu (ubuntu20.04, gcc11, shared, mpich)	17m 2s
docker (ubuntu-bionic)	8m 37s
windows (win2022, shared, serial)	13m 11s
linux_ubuntu (ubuntu20.04, clang6, shared, mpich)	10m 28s
linux_ubuntu (ubuntu20.04, clang10, shared, mpich)	14m 33s
windows (win2022, shared, ompi)	17m 1s
linux_ubuntu (ubuntu20.04, gcc8, ompi)	36m 3s
windows (win2022, static, serial, windows-2022, vs2022)	13m 24s
linux_ubuntu (ubuntu20.04, gcc8, serial)	9m 10s
linux_ubuntu (ubuntu20.04, clang6, ompi)	29m 13s
linux_ubuntu (ubuntu20.04, clang6, serial)	8m 5s
linux_ubuntu (ubuntu20.04, gcc8, static, ompi, build_only)	7m 36s
linux_ubuntu (ubuntu20.04, clang6, static, ompi, build_only)	4m 28s
linux_ubuntu (ubuntu20.04, gcc8, static, serial)	8m 6s
contract (examples)	2m 14s
contract (lammps)	4m 6s
contract (tau)	10m 59s
build_and_test	1s
	6h 39m 49s

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