CFLAGS for the host in canadian cross build

[Matias Fonzo]

On Mon, 6 Nov 2017 10:30:14 -0800
Max Filippov <jcmvbkbc@gmail.com> wrote:

> Hello,
> 
> I'm trying to build a canadian cross compiler with build ==
> x86_64-linux, host == xtensa-linux and target == xtensa-linux. I need
> to specify an xtensa-specific flag in CFLAGS that will be applied to
> the host binary.
> 
> I put this flag into CFLAGS and CXXFLAGS. The first question: is that
> the right place for it?
> 
> The build process tries to build libcpp for the build system and it
> runs x86_64 gcc with that xtensa-specific option. That's where the
> build breaks for me, because the option is not recognized by the
> build gcc. Is it supposed to work?
> 
> If CFLAGS/CXXFLAGS is the right place for the option, how can the
> build tell whether it's intended for the build or for the host?

GCC has $CFLAGS_FOR_BUILD and $CFLAGS_FOR_TARGET.