switch everything to the now-standardized thread_local

We're only using compilers new enough to support it now, so just use it
without a compatibility layer in between.

Change-Id: I97a24ed344e3d4ccde0b04af9c44995cf417a635
diff --git a/aos/common/libc/aos_strerror.cc b/aos/common/libc/aos_strerror.cc
index 4bca500..2c9735d 100644
--- a/aos/common/libc/aos_strerror.cc
+++ b/aos/common/libc/aos_strerror.cc
@@ -5,8 +5,6 @@
 #include <string.h>
 #include <stdio.h>
 
-#include "aos/linux_code/thread_local.h"
-
 // This code uses an overloaded function to handle the result from either
 // version of strerror_r correctly without needing a way to get the choice out
 // of the compiler/glibc/whatever explicitly.
@@ -35,7 +33,7 @@
 }  // namespace
 
 const char *aos_strerror(int error) {
-  static AOS_THREAD_LOCAL char buffer[kBufferSize];
+  static thread_local char buffer[kBufferSize];
 
   // Call the overload for whichever version we're using.
   return aos_strerror_handle_result(