ARM: compile everything with relro / bind_now.

Enable relro / bind_now when compiling Android applications.
This marks certain regions of memory as read-only after linking,
making memory corruption security vulnerabilities are harder
to exploit.

See:
 * http://www.akkadia.org/drepper/nonselsec.pdf (section 6)
 * http://tk-blog.blogspot.com/2009/02/relro-not-so-well-known-memory.html

Stop using the custom linker script, which inhibits
relro / bind_now support.

Change-Id: Ie97ccdd2845886bbc2ba2fdd47eed0ff4b29b60b