Hide emutls* symbols in libc.so

 Also make thread_local in test static to avoid ld.bfd
 warning for arm64.

Change-Id: I09a3f2aa9b73a4fafa3f3bbc64ddc2a128ad50ee
diff --git a/libc/Android.mk b/libc/Android.mk
index e632ee7..78b8475 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -1007,7 +1007,7 @@
 
 include $(CLEAR_VARS)
 LOCAL_SRC_FILES := $(libc_thread_atexit_impl_src_files)
-LOCAL_CFLAGS := $(libc_common_cflags) -fno-data-sections -Wframe-larger-than=2048
+LOCAL_CFLAGS := $(libc_common_cflags) -Wframe-larger-than=2048
 
 LOCAL_CONLYFLAGS := $(libc_common_conlyflags)
 LOCAL_CPPFLAGS := $(libc_common_cppflags) -Wold-style-cast