spack arch: add --family --generic flags (#47078) #453

Job	Run time
changes	28s
prechecks / style	57s
prechecks / validate	35s
prechecks / bootstrap-dev-rhel8	4m 15s
prechecks / import-check	1m 6s
prechecks / audit / package-audits (windows-latest, powershell Invoke-Expression -Command "./share/spack/qa/windows_t...	5m 40s
prechecks / audit / package-audits (ubuntu-latest, bash)	8m 15s
prechecks / audit / package-audits (macos-latest, bash)	5m 28s
all-prechecks	1s
bootstrap	0s
unit-tests	0s
coverage	0s
all	0s
	26m 45s

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