Experimental chisel7 support #450

Job	Run time
cancel-prior-workflows	3s
start-workflow	4s
filter-jobs-on-changes	8s
setup-persistent-repo	14m 3s
check-conda-lock-modified	0s
run-metasims-xilinx_alveo_u250	1s
build-default-bitstreams	1s
cleanup-local-fpga-repo	9s
run-basic-linux-poweroffs-xilinx_alveo_u250	1s
	14m 30s

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