[yocto] Changing HOST_CC_ARCH temporarily in recipe

[Mikko.Rapeli at bmw.de]

Hi,

On Wed, Sep 18, 2019 at 11:26:29AM +0300, Damien LEFEVRE wrote:
> Hi,
> 
> I have a package which requires to first build a x64 binary which is then
> used to compile the target platform binaries.
> 
> The way I got away with it was to build that host binary from
> do_configure_prepend() and then continue with the build procedure.
> 
> I recently upgraded to GCC7 + warrior and now building the host binary
> from do_configure_prepend fails due to this error:
> testCCompiler.c:1:0: error: bad value (armv8-a+crc) for -march= switch
> 
> I figured that the arch switch (building for tegra) is defined
> in HOST_CC_ARCH as:
> -march=armv8-a+crc -fstack-protector-strong  -D_FORTIFY_SOURCE=2 -Wformat
> -Wformat-security -Werror=format-security
> 
> If I clear HOST_CC_ARCH in my recipe file, do_configure_prepend succeeds
> but of course the rest of the build will fail.
> 
> So i'm trying to do something like this:
> do_configure_prepend(){
>     export HOST_CC_ARCH_BACKUP="${HOST_CC_ARCH}"
>     HOST_CC_ARCH=""
>     echo "HOST_CC_ARCH before cmake: ${HOST_CC_ARCH}"
>     CC="${BUILD_CC}" CXX="${BUILD_CXX}" CCFLAGS="${BUILD_CFLAGS}"
>  CXXFLAGS="${BUILD_CPPFLAGS} -std=c++11" LDFLAGS="${BUILD_LDFLAGS}" cmake
> ${S}
>     make
>     HOST_CC_ARCH="${HOST_CC_ARCH_BACKUP}"
> }
> 
> There I still get:
> HOST_CC_ARCH before cmake:  -march=armv8-a+crc -fstack-protector-strong
>  -D_FORTIFY_SOURCE=2 -Wformat -Wformat-security -Werror=format-security
> 
> So HOST_CC_ARCH doesn't get updated.
> 
> How can I temporarily reset HOST_CC_ARCH?

Only clean way to do this is to split the recipe into two parts:

 * native for the build time tooling

 * target for the target only build, which depends on the native build
   time tooling

Everything else is a hack :)

Hope this helps,

-Mikko