next-20250102: arm64: gcc-8-defconfig: Assembler messages: Error: unknown architectural extension `simd;'

[Naresh Kamboju]

The arm64 defconfig builds failed on the Linux next-20251002 tag build due
to following build warnings / errors with gcc-8 toolchain.

* arm64, build
  - gcc-8-defconfig

First seen on next-20251002
Good: next-20250929
Bad: next-20251002..next-20251003

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

Build regression: next-20250102: arm64: gcc-8-defconfig: Assembler
messages: Error: unknown architectural extension `simd;'

Reported-by: Linux Kernel Functional Testing <lkft at linaro.org>

### Build error log
/tmp/cclfMnj9.s: Assembler messages:
/tmp/cclfMnj9.s:656: Error: unknown architectural extension `simd;'
make[8]: *** [scripts/Makefile.build:287:
drivers/net/ethernet/mellanox/mlx5/core/wc.o] Error 1

Suspecting commit,
$ git blame -L 269 drivers/net/ethernet/mellanox/mlx5/core/wc.c
fd8c8216648cd8 (Patrisious Haddad 2025-09-29 00:08:08 +0300 269)
         (".arch_extension simd;\n\t"
fd8c8216648cd net/mlx5: Improve write-combining test reliability for
ARM64 Grace CPUs

## Source
* Kernel version: 6.17.0
* Git tree: https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next.git
* Git commit: 47a8d4b89844f5974f634b4189a39d5ccbacd81c
* Architectures: arm64
* Toolchains: gcc-8
* Kconfigs: defconfig

## Build
* Build log: https://storage.tuxsuite.com/public/linaro/lkft/builds/33YUHcFKTLSBTOxNIJqF9vJqcxt/build.log
* Build details:
https://regressions.linaro.org/lkft/linux-next-master/next-20251003/build/gcc-8-defconfig/
* Build plan: https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/builds/33YUHcFKTLSBTOxNIJqF9vJqcxt
* Build link: https://storage.tuxsuite.com/public/linaro/lkft/builds/33YUHcFKTLSBTOxNIJqF9vJqcxt/
* Kernel config:
https://storage.tuxsuite.com/public/linaro/lkft/builds/33YUHcFKTLSBTOxNIJqF9vJqcxt/config

--
Linaro LKFT