rust-cross-canadian: set CC_<triple> for nativesdk

This fixes build errors when building rust bindings for C dependencies
for the sdk host.
This will allow us to build and run rust programs on the sdk host.

Before:
% cargo build --target x86_64-oesdk-linux-gnu -vv
[...]
   Compiling zstd-sys v2.0.13+zstd.1.5.6 (zstd-rs/zstd-safe/zstd-sys)
[zstd-sys 2.0.13+zstd.1.5.6] CC_x86_64-oesdk-linux-gnu = None
[zstd-sys 2.0.13+zstd.1.5.6] CC = Some(arm-oe-linux-gnueabi-gcc  -mthumb -mfpu=neon -mfloat-abi=hard -mcpu=cortex-a7 -D_TIME_BITS=64 -D_FILE_OFFSET_BITS=64 --sysroot=/usr/local/sdk/sysroots/cortexa7t2hf-neon-oe-linux-gnueabi)
[zstd-sys 2.0.13+zstd.1.5.6] cargo:warning=ToolExecError: Command LC_ALL="C" "arm-oe-linux-gnueabi-gcc" "-mthumb" "-mfpu=neon" "-mfloat-abi=hard" "-mcpu=cortex-a7" "-D_TIME_BITS=64" "-D_FILE_OFFSET_BITS=64" "--sysroot=/usr/local/cc-sdk/sysroots/cortexa7t2hf-neon-oe-linux-gnueabi" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-gdwarf-4" "-fno-omit-frame-pointer" "-m64" "-I" "zstd/lib/" "-I" "zstd/lib/common" "-I" "zstd/lib/legacy" "-O2" "-pipe" "-g" "-feliminate-unused-debug-types" "-flto" "-ffat-lto-objects" "-fuse-linker-plugin" "-fvisibility=hidden" "-DZSTD_LIB_DEPRECATED=0" "-DXXH_PRIVATE_API=" "-DZSTDLIB_VISIBILITY=" "-DZDICTLIB_VISIBILITY=" "-DZSTDERRORLIB_VISIBILITY=" "-DZSTD_LEGACY_SUPPORT=1" "-o" "zstd-rs/target/x86_64-oesdk-linux-gnu/debug/build/zstd-sys-b2560022e172eec3/out/44ff4c55aa9e5133-debug.o" "-c" "zstd/lib/common/debug.c" with args arm-oe-linux-gnueabi-gcc did not execute successfully (status code exit status: 1).cargo:warning=arm-oe-linux-gnueabi-gcc: error: unrecognized command-line option '-m64'

After:
% cargo build --target x86_64-oesdk-linux-gnu -vv
[...]
   Compiling zstd-sys v2.0.13+zstd.1.5.6 (zstd-rs/zstd-safe/zstd-sys)
[zstd-sys 2.0.13+zstd.1.5.6] CC_x86_64_oesdk_linux_gnu = Some(x86_64-oesdk-linux-gcc)
[...]
   Compiling zstd v0.13.2 (zstd-rs)
    Finished dev [unoptimized + debuginfo] target(s) in 14.67s

Signed-off-by: Sean Nyekjaer <sean@geanix.com>
---
 meta/recipes-devtools/rust/rust-cross-canadian.inc | 2 ++
 1 file changed, 2 insertions(+)

Hi Sean,

> On 14 Jan 2025, at 08:21, Sean Nyekjaer via lists.openembedded.org <sean=geanix.com@lists.openembedded.org> wrote:
> 
> This fixes build errors when building rust bindings for C dependencies
> for the sdk host.
> This will allow us to build and run rust programs on the sdk host.

Can you also add a test case to exercise this, to ensure it doesn’t regress in the future?  meta/lib/oeqa/sdk/cases/rust.py has some minimal testing already so adding more there would be great.

> --- a/meta/recipes-devtools/rust/rust-cross-canadian.inc
> +++ b/meta/recipes-devtools/rust/rust-cross-canadian.inc
> @@ -58,11 +58,13 @@ do_install () {
> 
>     RUST_TARGET_TRIPLE=`echo ${RUST_TARGET_SYS} | tr '[:lower:]' '[:upper:]' | sed 's/-/_/g'`
>     RUST_HOST_TRIPLE=`echo ${RUST_HOST_SYS} | tr '[:lower:]' '[:upper:]' | sed 's/-/_/g'`
> +    RUST_HOST_CC=`echo ${RUST_HOST_SYS} | sed 's/-/_/g'`
>     SDKLOADER=${@bb.utils.contains('SDK_ARCH', 'x86_64', 'ld-linux-x86-64.so.2', '', d)}${@bb.utils.contains('SDK_ARCH', 'i686', 'ld-linux.so.2', '', d)}${@bb.utils.contains('SDK_ARCH', 'aarch64', 'ld-linux-aarch64.so.1', '', d)}${@bb.utils.contains('SDK_ARCH', 'ppc64le', 'ld64.so.2', '', d)}${@bb.utils.contains('SDK_ARCH', 'riscv64', 'ld-linux-riscv64-lp64d.so.1', '', d)}
> 
>     cat <<- EOF > "${RUST_ENV_SETUP_SH}"
> export CARGO_TARGET_${RUST_TARGET_TRIPLE}_RUSTFLAGS="--sysroot=\$OECORE_TARGET_SYSROOT/usr -C link-arg=--sysroot=\$OECORE_TARGET_SYSROOT"
> export CARGO_TARGET_${RUST_HOST_TRIPLE}_RUNNER="\$OECORE_NATIVE_SYSROOT/lib/${SDKLOADER}"
> + export CC_$RUST_HOST_CC="${CCACHE}${HOST_PREFIX}gcc"
> export RUST_TARGET_PATH="\$OECORE_NATIVE_SYSROOT/usr/lib/${TARGET_SYS}/rustlib”
> EOF

There’s another series on the list that rewrites this (https://lore.kernel.org/openembedded-core/20250116134833.1838212-1-Harish.Sadineni@windriver.com/) and moves some assignments to an environment file in rust.bb.  I suspect the same needs to happen here, so can you rebase on top of that patch (or wait for that to be merged and rebase).

Thanks,
Ross