Allow "lite" Chipyard builds with a minimal subset of submodules #434

Job	Run time
cancel-prior-workflows	3s
start-workflow	2s
filter-jobs-on-changes	6s
setup-persistent-repo	17m 19s
check-conda-lock-modified	0s
run-metasims-xilinx_alveo_u250	5s
cleanup-local-fpga-repo	10s
build-default-bitstreams	0s
run-basic-linux-poweroffs-xilinx_alveo_u250	0s
	17m 45s

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