As of version 6.0 Android does not support hard links.

diff -u -r ../postgresql-9.6.2/src/include/pg_config_manual.h ./src/include/pg_config_manual.h
--- ../postgresql-9.6.2/src/include/pg_config_manual.h	2017-02-06 22:45:25.000000000 +0100
+++ ./src/include/pg_config_manual.h	2017-03-05 12:18:44.630725191 +0100
@@ -124,7 +124,7 @@
 /*
  * Define this if your operating system supports link()
  */
-#if !defined(WIN32) && !defined(__CYGWIN__)
+#if !defined(WIN32) && !defined(__CYGWIN__) && !defined(__ANDROID__)
 #define HAVE_WORKING_LINK 1
 #endif