test: add a compiledir pattern in run.go

The compiledir pattern compiles all files xxx.dir/*.go
in lexicographic order (which is assumed to coincide with
the topological order of dependencies).

R=rsc
CC=golang-dev, remy
https://golang.org/cl/6440048
diff --git a/test/fixedbugs/bug088.go b/test/fixedbugs/bug088.go
index 9715a70..3b99da8 100644
--- a/test/fixedbugs/bug088.go
+++ b/test/fixedbugs/bug088.go
@@ -1,4 +1,4 @@
-// $G $D/$F.dir/bug0.go && $G $D/$F.dir/bug1.go || echo BUG: fails incorrectly
+// compiledir
 
 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style