[scarthgap-clang20] sdk build fails to build libclc

[cmeissl]

When trying to build a sdk using the scarthgap-clang20 the build fails on libclc.

Error reported by bitbake indicates some issue with prepare_builtins:

...
| /build/tmp-glibc/work/x86_64-nativesdk-av2sdk-linux/nativesdk-libclc/20.1.1/recipe-sysroot-native/usr/bin/opt: WARNING: failed to create target machine for 'spir-unknown-unknown': unable to get target for 'spir-unknown-unknown', see --version and --triple.
| [998/3493] cd /build/tmp-glibc/work/x86_64-nativesdk-av2sdk-linux/nativesdk-libclc/20.1.1/build && prepare_builtins -o clspv--.bc /build/tmp-glibc/work/x86_64-nativesdk-av2sdk-linux/nativesdk-libclc/20.1.1/build/builtins.opt.clspv--.bc
| FAILED: clspv--.bc /build/tmp-glibc/work/x86_64-nativesdk-av2sdk-linux/nativesdk-libclc/20.1.1/build/clspv--.bc
| cd /build/tmp-glibc/work/x86_64-nativesdk-av2sdk-linux/nativesdk-libclc/20.1.1/build && prepare_builtins -o clspv--.bc /build/tmp-glibc/work/x86_64-nativesdk-av2sdk-linux/nativesdk-libclc/20.1.1/build/builtins.opt.clspv--.bc
| /bin/sh: 1: prepare_builtins: not found
...

The build output seems to contain the binary prepare_builtins, but can't be run on the build host.
Afaict the reason seems to be that it tries to use a non existing interpreter /usr/local/oe-sdk-hardcoded-buildpath/sysroots/x86_64-av2sdk-linux/lib/ld-linux-x86-64.so.2

[kraj]

Can you try this patch to libclc which is proposed from oe-core

https://patchwork.yoctoproject.org/project/oe-core/patch/20250730061807.1642753-1-raj.khem@gmail.com/

[cmeissl]

The recipe libclc_git.bb in the scarthgap-clang20 branch does not define the function do_build_prepare_builtins().
I tried to override the whole recipe with the version from oe and add export LDFLAGS="${BUILD_LDFLAGS}", but it seems to result in the same issue.

[kraj]

The recipe libclc_git.bb in the scarthgap-clang20 branch does not define the function do_build_prepare_builtins(). I tried to override the whole recipe with the version from oe and add export LDFLAGS="${BUILD_LDFLAGS}", but it seems to result in the same issue.

yeah the problem is that its using nativesdk flags to override it. so this has to be done surgically, perhaps patch the build of libclc