cc/gcc: add an option to enable/disable build of libssp

libssp is the run-time Stack-Smashing Protection library.
It can be usefull to have or miss, depends...

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 reporter_name="Yann E. MORIN"

 reporter_url="http://ymorin.is-a-geek.org/projects/crosstool"

 reporter_comment="EXPERIMENTAL MIPS-64 n64 toolchain."