The selftests x86_64 builds failed due to following build warnings / errors on the Linux next-20251020 and next-20251021 tags with gcc-14 and clang-21.

First seen on next-20251020 Good: next-20251020 Bad: next-20251017

Regression Analysis: - New regression? yes - Reproducibility? yes

### Build errors x86_64-linux-gnu-gcc -m64 -o kselftest/x86/single_step_syscall_64 -O2 -g -std=gnu99 -pthread -Wall -isystem usr/include -no-pie -DCAN_BUILD_64 single_step_syscall.c -lrt -ldl In file included from single_step_syscall.c:34: helpers.h:10:10: fatal error: kselftest.h: No such file or directory 10 | #include "kselftest.h" | ^~~~~~~~~~~~~ compilation terminated. make[4]: *** [Makefile:86: kselftest/x86/single_step_syscall_64] Error 1

### Suspected patch git log --oneline next-20251017..next-20251020 -- tools/testing/selftests/x86/ 4d89827dfb274 selftests: complete kselftest include centralization

Build regressions: next-20251020: selftests: helpers.h:10:10: fatal error: kselftest.h: No such file or directory

Reported-by: Linux Kernel Functional Testing lkft@linaro.org

### Steps to reproduce - tuxmake --runtime podman --target-arch x86_64 --toolchain gcc-14 \ --kconfig https://storage.tuxsuite.com/public/linaro/lkft/builds/34JgN0fZ9uXj6HVnjvjqz... \ debugkernel cpupower headers kernel kselftest modules

## Source * Kernel version: 6.18.0-rc2 * Git tree: https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next.git * Git describe: next-20251021 and next-20251020 * Git commit: fe45352cd106ae41b5ad3f0066c2e54dbb2dfd70 * Architectures: x86_64 * Toolchains: gcc-14 and clang-21 * Kconfigs: defconfig+selftests/*/configs

## Build * Build log: https://storage.tuxsuite.com/public/linaro/lkft/builds/34JgN0fZ9uXj6HVnjvjqz... * Build details: https://regressions.linaro.org/lkft/linux-next-master/next-20251020/kselftes... * Build link: https://storage.tuxsuite.com/public/linaro/lkft/builds/34JgN0fZ9uXj6HVnjvjqz... * Kernel config: https://storage.tuxsuite.com/public/linaro/lkft/builds/34JgN0fZ9uXj6HVnjvjqz...

-- Linaro LKFT https://lkft.linaro.org