add fortified readlink/readlinkat implementations

Change-Id: Ia4b1824d20cad3a072b9162047492dade8576779
diff --git a/libc/Android.mk b/libc/Android.mk
index 9d3b62a..814940c 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -74,6 +74,8 @@
     bionic/__pread64_chk.cpp \
     bionic/__pread_chk.cpp \
     bionic/__read_chk.cpp \
+    bionic/__readlink_chk.cpp \
+    bionic/__readlinkat_chk.cpp \
     bionic/__recvfrom_chk.cpp \
     bionic/__stpcpy_chk.cpp \
     bionic/__stpncpy_chk.cpp \