resources: Re-publish on transformation cache hit

When a resource transformation result was served from cache (same
options as a previous build), the output file was not re-written to
disk. This caused incorrect output when toggling transformation
options (e.g. minify) back to a previously seen value in server mode.

Fixes #14629

identity/identity.go

@@ -245,6 +245,11 @@ type SignalRebuilder interface {
 	SignalRebuild(ids ...Identity)
 }
 
+// IsRebuildProvider signals if we're in a rebuild or not.
+type IsRebuildProvider interface {
+	IsRebuild() bool
+}
+
 // IncrementByOne implements Incrementer adding 1 every time Incr is called.
 type IncrementByOne struct {
 	counter uint64