fixed lots of not-thread-safe things

Most of the things I fixed here were using libc functions that are
fundamentally not thread-safe.
diff --git a/aos/build/aos.gyp b/aos/build/aos.gyp
index 916db03..3aaaf10 100644
--- a/aos/build/aos.gyp
+++ b/aos/build/aos.gyp
@@ -25,10 +25,10 @@
       ],
       'dependencies': [
         '<(AOS)/common/common.gyp:die',
-        '<(AOS)/common/util/util.gyp:aos_strerror',
+        '<(AOS)/common/libc/libc.gyp:aos_strerror',
       ],
       'export_dependent_settings': [
-        '<(AOS)/common/util/util.gyp:aos_strerror',
+        '<(AOS)/common/libc/libc.gyp:aos_strerror',
       ],
     },
     {