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>
(transplanted from e3e1c9d45bddfbfb433ee9d583faf42fa31f50c0)
1 reporter_name="dsreed on freenode/#crosstool-ng"
3 reporter_comment="Enables experimental support for VFP/NEON hardware floating point."