Yocto cross-compilation broken with Rust & CMake

[tronical]

After commit 1830042 , slint-compiler invokes a configure script for jemalloc which seems to use autoconf to cross-compile.

When building within a Yocto environment, CC, etc. are set to the target compiler, and during the Slint-cpp crate build we have some build scripts that use cc.rs to build for the host. Therefore we set CC_${host} and cc.rs uses that instead.

As per 3c37c51 the same trick would work for jemalloc's configure to get past checking whether the C compiler works... no, but then we hit this:

  checking how to run the C preprocessor... aarch64-poky-linux-gcc -E  -mcpu=cortex-a57 -march=armv8-a+crc -fstack-protector-strong  -O2 -D_FORTIFY_SOURCE=2 -Wformat -Wformat-security -Werror=format-security --sysroot=/home/runner/work/slint/yocto-sdk/sysroots/cortexa57-poky-linux

and that can't work.

[tronical]

I tried setting HOST_CPP in bbc25d4 but that didn't help:

https://github.com/slint-ui/slint/actions/runs/12973562980/job/36182368807

same error.

[tronical]

Same problem with CPP_$target:

b1e5761

[ogoffart]

Maybe we need to make a change in corrosion?
We can also make the jemalloc a feature in slint-compiler and not enable it when cross compiling.
Or we just don't use jemalloc in the slint-compiler at all, that is not performance critical.

[tronical]

I think upstream needs to be fixed (maybe just the crate).

I think a feature makes sense, and we opt in for the binaries that we build in the CI.