Fix strace build by building "ldt.c".

Change-Id: I70843b3a12467baec0e988c366ce48adfa2567ab
diff --git a/Android.mk b/Android.mk
index d864fde..18d1d1d 100644
--- a/Android.mk
+++ b/Android.mk
@@ -37,6 +37,7 @@
     ipc.c \
     kexec.c \
     keyctl.c \
+    ldt.c \
     loop.c \
     mem.c \
     mtd.c \