return
				}
			}
		}()
	}

	wg.Wait()

	// Write action graph again, this time with timing information.
	writeActionGraph()
}

// buildActionID computes the action ID for a build action.
func (b *Builder) buildActionID(a *Action) cache.ActionID {
	p := a.Package
	h := cache.NewHash("build " + p.ImportPath)

	// Configuration independent of compiler toolchain.