Replace non-portable regex #301

Job	Run time
define-matrix	5s
build (yosys-0.44)	2m 17s
build (0.45)	2m 18s
build (0.46)	2m 21s
build (0.47)	2m 20s
build (v0.48)	2m 23s
build (v0.49)	2m 20s
test (yosys-0.44)	1m 38s
test-croc-boot (yosys-0.44)	4m 7s
test (0.45)	51s
test-compat (yosys-0.44, black-parrot)	1m 7s
test (0.46)	50s
test-croc-boot (v0.49)	3m 8s
test-compat (yosys-0.44, bsc-core_tile)	1m 42s
test (0.47)	51s
test-compat (yosys-0.44, cv32e40p)	55s
test (v0.48)	56s
test-compat (yosys-0.44, ibex)	50s
test (v0.49)	54s
test-compat (yosys-0.44, opentitan)	2m 52s
test-compat (yosys-0.44, rsd)	54s
test-compat (v0.49, black-parrot)	1m 10s
test-compat (v0.49, bsc-core_tile)	1m 1s
test-compat (v0.49, cv32e40p)	53s
test-compat (v0.49, ibex)	1m 18s
test-compat (v0.49, opentitan)	3m 7s
test-compat (v0.49, rsd)	55s
	44m 3s

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