security_flags: Add the compiler and linker flags that enhance security

security_flags: Add the compiler and linker flags that enhance security

These flags add addition checks at compile, link and runtime to prevent
stack smashing, checking for buffer overflows, and link at program start
to prevent call spoofing later.

This needs to be explicitly enabled by adding the following line to your
local.conf:

require conf/distro/include/security_flags.inc

[YOCTO #3868]

(From OE-Core rev: ff0e863f2d345c42393a14a193f76d699745a2b9)

Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>