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

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>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>