internal/pkg: exclusive artifacts

This alleviates scheduler overhead when curing many artifacts.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/etc.go

@@ -89,6 +89,9 @@ func (cureEtc) Kind() pkg.Kind { return kindEtc }
 // Params is a noop.
 func (cureEtc) Params(*pkg.IContext) {}
 
+// IsExclusive returns false: Cure performs a few trivial filesystem writes.
+func (cureEtc) IsExclusive() bool { return false }
+
 // Dependencies returns a slice containing the backing iana-etc release.
 func (a cureEtc) Dependencies() []pkg.Artifact {
 	if a.iana != nil {