all: merge NaCl branch (part 1)

src/cmd/go/test.go

 // Copyright 2011 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 package main
 
 import (
         "bytes"
         "fmt"
         "go/ast"
@@ skipping 275 matching lines @@
 var testMainDeps = map[string]bool{
         // Dependencies for testmain.
         "testing": true,
         "regexp":  true,
 }
 
 func runTest(cmd *Command, args []string) {
         var pkgArgs []string
         pkgArgs, testArgs = testFlags(args)
 
+        findExecCmd() // initialize cached result
+
         raceInit()
         pkgs := packagesForBuild(pkgArgs)
         if len(pkgs) == 0 {
                 fatalf("no packages to test")
         }
 
         if testC && len(pkgs) != 1 {
                 fatalf("cannot use -c flag with multiple packages")
         }
         if testProfile && len(pkgs) != 1 {
@@ skipping 522 matching lines @@
                         File: filepath.Join(importPath, file),
                         Var:  fmt.Sprintf("GoCover_%d", coverIndex),
                 }
                 coverIndex++
         }
         return coverVars
 }
 
 // runTest is the action for running a test binary.
 func (b *builder) runTest(a *action) error {
-        args := stringList(a.deps[0].target, testArgs)
+        args := stringList(findExecCmd(), a.deps[0].target, testArgs)
         a.testOutput = new(bytes.Buffer)
 
         if buildN || buildX {
                 b.showcmd("", "%s", strings.Join(args, " "))
                 if buildN {
                         return nil
                 }
         }
 
         if a.failed {
@@ skipping 374 matching lines @@
                 Mode: {{printf "%q" .CoverMode}},
                 Counters: coverCounters,
                 Blocks: coverBlocks,
                 CoveredPackages: {{printf "%q" .Covered}},
         })
 {{end}}
         testing.Main(matchString, tests, benchmarks, examples)
 }
 
 `))