Check for -fstack-protector

Check for -fstack-protector

Not all toolchains provide support for -fstack-protector. This patch
provides a configure check to avoid build errors like

/home/buildroot/buildroot/output/host/opt/ext-toolchain/bin/../lib/gcc/x86_64-buildroot-linux-uclibc/6.4.0/../../../../x86_64-buildroot-linux-uclibc/bin/ld: cannot find -lssp_nonshared
/home/buildroot/buildroot/output/host/opt/ext-toolchain/bin/../lib/gcc/x86_64-buildroot-linux-uclibc/6.4.0/../../../../x86_64-buildroot-linux-uclibc/bin/ld: cannot find -lssp