misc/nacl: fix build

Add gofmt.go and gofmt_test.go as they are part of the test data set.

See CL 130440043.

LGTM=dvyukov
R=golang-codereviews, dvyukov
CC=golang-codereviews
https://golang.org/cl/132820044

misc/nacl/testzip.proto

@@ -14,6 +14,8 @@ go	src=..
 				objfile
 					objfile.go
 			gofmt
+				gofmt.go
+				gofmt_test.go
 				testdata
 					+
 			link