Reapply directory error handling change.

runtime/bin/platform_macos.cc

Index: runtime/bin/platform_macos.cc
diff --git a/runtime/bin/platform_macos.cc b/runtime/bin/platform_macos.cc
index aee6f89200291c56e4971b66b03f0c06372805c7..02745aa77b1cba756e11fe6686855e4586ebe24a 100644
--- a/runtime/bin/platform_macos.cc
+++ b/runtime/bin/platform_macos.cc
@@ -4,6 +4,7 @@
 
 #include "bin/platform.h"
 
+#include <string.h>
 #include <unistd.h>
 
 
@@ -15,3 +16,12 @@ int Platform::NumberOfProcessors() {
 const char* Platform::OperatingSystem() {
   return "macos";
 }
+
+
+char* Platform::StrError(int error_code) {
+  static const int kBufferSize = 1024;
+  char* error = static_cast<char*>(malloc(kBufferSize));
+  error[0] = '\0';
+  strerror_r(error_code, error, kBufferSize);
+  return error;
+}