vendor._gowin: Add 'add_preferences' override #3580

Job	Run time
check-links	46s
document	46s
smoke (amaranth-lang/amaranth-boards)	34s
test (3.8)	2m 21s
smoke (amaranth-lang/amaranth-stdio)	42s
test (3.9)	2m 25s
smoke (amaranth-lang/amaranth-soc)	43s
test (3.10)	2m 15s
test (3.11)	3m 1s
test (3.12)	3m 34s
test (pypy-3.8)	5m 31s
test (pypy-3.9)	5m 12s
test (pypy-3.10)	6m 10s
test (3.13-dev)	3m 14s
publish-docs	9s
publish-docs-dev	0s
required	1s
publish-schemas	5s
publish-package	38s
publish-release	0s
	38m 7s

Provide feedback