Remove libstdc++ tests from toolchain_tests
Remove libstdc++ tests from toolchain_tests

Remove the special handling in toolchain_tests for libstdc++
with PNaCl, in preparation for removing libstdc++ itself.

R=jfb@chromium.org

Review URL: https://codereview.chromium.org/1076633002

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client