Avoid strerror_r portability issues

runtime/vm/os_thread_macos.cc

Index: runtime/vm/os_thread_macos.cc
diff --git a/runtime/vm/os_thread_macos.cc b/runtime/vm/os_thread_macos.cc
index 851a4678ab6f783424eb877befcc7fcfae1384d5..fad1cc5a1a967f1aa0a4923e1111dc922e65d8cc 100644
--- a/runtime/vm/os_thread_macos.cc
+++ b/runtime/vm/os_thread_macos.cc
@@ -19,6 +19,7 @@
 #include <mach/thread_act.h>  // NOLINT
 
 #include "platform/assert.h"
+#include "platform/utils.h"
 
 namespace dart {
 
@@ -26,7 +27,7 @@ namespace dart {
   if (result != 0) { \
     const int kBufferSize = 1024; \
     char error_message[kBufferSize]; \
-    strerror_r(result, error_message, kBufferSize); \
+    Utils::StrError(result, error_message, kBufferSize); \
     FATAL2("pthread error: %d (%s)", result, error_message); \
   }
 
@@ -44,7 +45,7 @@ namespace dart {
   if (result != 0) { \
     const int kBufferSize = 1024; \
     char error_message[kBufferSize]; \
-    strerror_r(result, error_message, kBufferSize); \
+    Utils::StrError(result, error_message, kBufferSize); \
     fprintf(stderr, "%s:%d: pthread error: %d (%s)\n", \
             __FILE__, __LINE__, result, error_message); \
     return result; \