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="Remy Bohmer"
2 reporter_url="linux@bohmer.net"
3 reporter_comment="Example for building a toolchain for m68000 bare metal targets"