[x86] Changes and Additions to fix broken x86 build

Add missing syscalls to android/libc/arch-x86/syscalls

Remove #undef HAVE_GETLINE from platform.h
Fixes definition conflict warnings for x86 but is also
suitable for arm as  bionic has had a getline implementation for a
while now

Remove hardcoded CONFIG_CROSS_COMPILER_PREFIX from .config-full
and .config-minimal. This is now appended to  .config as part of
the prepare target in Android.mk

It appears no other changes are needed to other files such as
bbconfigopts.h etc as these are autogenerated when make prepare
is run.

Android.mk:
Added missing syscalls source to BUSYBOX_SRC_FILES when
TARGET_ARCH=x86.
Added appending of the CONFIG_CROSS_COMPILER_PREFIX to the .config
file based on the TARGET_ARCH

Change-Id: I4f550757b3209b852cd5a017e88dce50678e5734
enable SELinux

require external/libsepol static lib patch

Signed-off-by: Tanguy Pruvot <tanguy.pruvot@gmail.com>

Change-Id: I4076da694a6192b44b3f143c095e8990a9a6efa9
selinux: bionic support for restorecon/setfiles

Change-Id: I5230197c3363a53ec73f038d85a73b384fd98103
update config

Change-Id: I601e12058d5ac53f040a8fa55c7e061d54d76d29