Fix Solaris link_a and link_o

A long time ago, Solaris cc didn't seem to handle -Wl, linker options,
while gcc on Solaris required it.  Since then, Solaris cc has
developed to understand -Wl, options, and our little dance to figure
out how to pass linker options to the C compiler that's used isn't
needed any more.

Reviewed-by: Andy Polyakov <appro@openssl.org>