Solaris Studio 12.3 build and link fix.

Solaris Studio 12.3 does not output `Sun` in their `-flags` option any more.
While `-library=sunperf` option is avaiable, so add `i` option into regexp for checking environment.

I'm not sure why, but Solaris Studio 12.3 `CC` didn't link `libCstd` in this program.
So added the linking option in the `extconf.rb`.