Experimental chisel7 support #449

Job	Run time
cancel-prior-workflows	5s
start-workflow	2s
filter-jobs-on-changes	5s
setup-persistent-repo	46s
check-conda-lock-modified	-1s
run-metasims-xilinx_alveo_u250	1s
run-basic-linux-poweroffs-xilinx_alveo_u250	1s
build-default-bitstreams	1s
cleanup-local-fpga-repo	4s
	1m 4s

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