List of comma-separated regular expressions, each optionally prefixed by - (negative expression), assigned (=) to a list of comma-separated constraint value targets. If a target matches no negative expression and at least one positive expression its toolchain resolution will be performed as if it had declared the constraint values as execution constraints. Example: //demo,- test=@platforms//cpus:x86_64 will add 'x86_64' to any target under //demo except for those whose name contains 'test'.