libc.so dependency on libssp_nonshared.a

[Gleb Kurtsou]

I came across some build issues in libc.so and SSP.

libc.ldscript (aka libc.so) unconditionally includes @@LIBDIR@@/libssp_nonshared.a

libssp* are not built if WITHOUT_SSP defined.

ObsoleteFiles.inc doesn't mention libssp*.

Consider WITHOUT_SSP=yes case.  As soon as one does clean installworld
and/or removes stale libssp_nonshared.a ld fails to link anything
because of missing libssp_nonshared.a

libc.so during buildworld (as found under /usr/obj) is symlink to the
actual shared library, but not ldscript.  Is it intentional?  I wouldn't
expect make -C /usr/src/bin/cat to match buildworld result closely
assuming src and world are in sync, but they seem to have different idea
of what libc is..