Compile fts.c in libc_openbsd_ndk

fts.c is from openbsd and has compatibility macros to make it compile
as part of bionic.  Move it into libc_openbsd_ndk where it will
get the workarounds from -include openbsd-compat.h instead.

Test: m libc
Change-Id: I213d423af8f010e39460b611e902acbf3561ae7a
diff --git a/libc/Android.bp b/libc/Android.bp
index fbf7ec2..4f5089e 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -24,7 +24,6 @@
     "bionic/ether_aton.c",
     "bionic/ether_ntoa.c",
     "bionic/exit.cpp",
-    "bionic/fts.c",
     "bionic/initgroups.c",
     "bionic/isatty.c",
     "bionic/sched_cpualloc.c",
@@ -565,6 +564,10 @@
         "upstream-openbsd/lib/libc/string/strxfrm.c",
         "upstream-openbsd/lib/libc/string/wcslcpy.c",
         "upstream-openbsd/lib/libc/string/wcswidth.c",
+
+        // This file is originally from OpenBSD, and benefits from
+        // being compiled with openbsd-compat.h.
+        "bionic/fts.c",
     ],
 
     cflags: [