cc/gcc: Apply CT_CC_GCC_DISABLE_PCH to do_cc_core.
Otherwise, users have to input --disable-libstdcxx-pch option
when building bare-metal CANADIAN C++ compiler.
Reviewed-by: Michael Hope
Signed-off-by: Zhenqiang Chen <zhenqiang.chen@linaro.org>
1 reporter_name="Gustavo Zacarias <gustavo@zacarias.com.ar>"
2 reporter_url="http://sourceware.org/ml/crossgcc/2011-03/msg00028.html"