Hard-wire the path to xcrun as /usr/bin/xcrun.

This lets us not leak $PATH to soong_build. It was only needed for
Darwin tests anyway.

Test: Will ask jingwen@ who has a Mac.
Change-Id: I4647e41275b323fe6283580f8f92718c6229f23e

android/config.go

@@ -527,25 +527,6 @@ func (c *config) HostJavaToolPath(ctx PathContext, path string) Path {
 	return PathForOutput(ctx, "host", c.PrebuiltOS(), "framework", path)
 }
 
-// NonHermeticHostSystemTool looks for non-hermetic tools from the system we're
-// running on. These tools are not checked-in to AOSP, and therefore could lead
-// to reproducibility problems. Should not be used for other than finding the
-// XCode SDK (xcrun, sw_vers), etc. See ui/build/paths/config.go for the
-// allowlist of host system tools.
-func (c *config) NonHermeticHostSystemTool(name string) string {
-	for _, dir := range filepath.SplitList(c.Getenv("PATH")) {
-		path := filepath.Join(dir, name)
-		if s, err := os.Stat(path); err != nil {
-			continue
-		} else if m := s.Mode(); !s.IsDir() && m&0111 != 0 {
-			return path
-		}
-	}
-	panic(fmt.Errorf(
-		"Cannot find non-hermetic system tool '%s' on path '%s'",
-		name, c.Getenv("PATH")))
-}
-
 // PrebuiltOS returns the name of the host OS used in prebuilts directories.
 func (c *config) PrebuiltOS() string {
 	switch runtime.GOOS {

cc/config/x86_darwin_host.go

@@ -136,7 +136,7 @@ var macTools = &macPlatformTools{}
 
 func getMacTools(ctx android.PackageVarContext) *macPlatformTools {
 	macTools.once.Do(func() {
-		xcrunTool := ctx.Config().NonHermeticHostSystemTool("xcrun")
+		xcrunTool := "/usr/bin/xcrun"
 
 		xcrun := func(args ...string) string {
 			if macTools.err != nil {

ui/build/soong.go

@@ -177,14 +177,6 @@ func runSoong(ctx Context, config Config) {
 		ninjaEnv.Set("TOP", os.Getenv("TOP"))
 		ninjaEnv.Set("SOONG_OUTDIR", config.SoongOutDir())
 
-		// Needed for NonHermeticHostSystemTool() and that, only in tests. We should
-		// probably find a better way of running tests other than making $PATH
-		// available also to production builds. Note that this is not get same as
-		// os.Getenv("PATH"): config.Environment() contains the $PATH that redirects
-		// every binary through the path interposer.
-		configPath, _ := config.Environment().Get("PATH")
-		ninjaEnv.Set("PATH", configPath)
-
 		// For debugging
 		if os.Getenv("SOONG_DELVE") != "" {
 			ninjaEnv.Set("SOONG_DELVE", os.Getenv("SOONG_DELVE"))