Support multiple rsp files in RuleBuilder

The lint rule is manually creating a second rsp file because Ninja
only supports on per rule.  Move the support into RuleBuilder so
that it can apply the same rewrites that it does to the primary
one.

Test: TestRuleBuilder_Build
Change-Id: Iec250a2d60e74ccf1b4ad085a960fec6867ea559

java/java_test.go

@@ -628,7 +628,7 @@ prebuilt_stubs_sources {
 	}
 
 	t.Run("empty/missing directory", func(t *testing.T) {
-		test(t, "empty-directory", []string{})
+		test(t, "empty-directory", nil)
 	})
 
 	t.Run("non-empty set of sources", func(t *testing.T) {