Add UM version to fiat, using the ACCESS-NRI/fiat repo and CMake environment variables #26

Job	Run time
changes	3s
prechecks / validate	34s
prechecks / style	53s
prechecks / bootstrap-dev-rhel8	3m 50s
prechecks / audit / package-audits (windows-latest, powershell Invoke-Expression -Command "./share/spack/qa/windows_t...	2m 34s
prechecks / audit / package-audits (ubuntu-latest, bash)	1m 49s
prechecks / audit / package-audits (macos-latest, bash)	1m 9s
all-prechecks	1s
bootstrap	0s
unit-tests	0s
all	0s
	10m 53s

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