devel/linux-c6-devtools: add libstdc++

[xmj]

Summary

Currently, linux-c6-devtools misses libstdc++, which makes compilation of Linux
C++ code impossible. Fix this by adding the i686 libraries.

devel/linux-c6-devtools: add libstdc++

- Add c6 libstdc++ RPM, so that Linux C++ code can be compiled.

PR:	194360
(DiffRev: placeholder)
Submitted by:	brooks
Approved by:	swills (mentor)

Test Plan

http://xmj.me/freebsd/buildlogs/linux-c6-devtools-6.5_1.log

[xmj]

Symlink contrib/linux/usr/lib/gcc/i686-redhat-linux/4.4.4/libgcc_s.so to
/compat/linux/lib/libgcc_s.so.1

I've updated the buildlog in the original description, so the URL stays the same -- still builds.

[brooks]

As zmj pointed out in the PR, I'm not using any make conditionals so bsd.port.mk alone does work fine.

[swills]

Approved!

[xmj]

Committed revision 371057.