cmd/go: fix typo in test inputs descriptor

Presumably each line in the descriptor should match the corresponding operation.

Change-Id: I7726befcd62147324764d15c26e737357122be51
GitHub-Last-Rev: 85e610e3045950b8688a7a506b37a2a92ac7445c
GitHub-Pull-Request: golang/go#24807
Reviewed-on: https://go-review.googlesource.com/106355Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/go/internal/test/test.go

@@ -1487,7 +1487,7 @@ func computeTestInputsID(a *work.Action, testlog []byte) (cache.ActionID, error)
 			fmt.Fprintf(h, "env %s %x\n", name, hashGetenv(name))
 		case "chdir":
 			pwd = name // always absolute
-			fmt.Fprintf(h, "cbdir %s %x\n", name, hashStat(name))
+			fmt.Fprintf(h, "chdir %s %x\n", name, hashStat(name))
 		case "stat":
 			if !filepath.IsAbs(name) {
 				name = filepath.Join(pwd, name)