rustgcc-kselftest: error: unknown unstable option: `patchable-function-entry`

[Naresh Kamboju]

The x86 rust gcc builds failed on the Linux next-20240917 due to following build
warnings / errors with rustgcc for selftests rust builds.

First seen on next-20240917
  Good: next-20240913
  BAD:  next-20240917

Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>

build log:
--------
error: unknown unstable option: `patchable-function-entry`

make[3]: *** [rust/Makefile:392: rust/core.o] Error 1

Build Log links,
--------
 - https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20240916/testrun/25144919/suite/build/test/rustgcc-lkftconfig-kselftest/log

Build failed comparison:
 - https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20240916/testrun/25144919/suite/build/test/rustgcc-lkftconfig-kselftest/history/

metadata:
----
  git describe: next-20240917
  git repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next
  git sha: 7083504315d64199a329de322fce989e1e10f4f7
  kernel config:
https://storage.tuxsuite.com/public/linaro/lkft/builds/2m9CHpK6gWVXL2Rjt0R5TdMRwKg/config
  build url: https://storage.tuxsuite.com/public/linaro/lkft/builds/2m9CHpK6gWVXL2Rjt0R5TdMRwKg/
  toolchain: rustgcc
  config-name: rustgcc-lkftconfig-kselftest
  arch: x86

Steps to reproduce:
---------
 - https://storage.tuxsuite.com/public/linaro/lkft/builds/2m9CHpK6gWVXL2Rjt0R5TdMRwKg/tuxmake_reproducer.sh
 - tuxmake --runtime podman \
           --target-arch x86_64 \
           --toolchain rustgcc \
           --kconfig
https://storage.tuxsuite.com/public/linaro/lkft/builds/2m9CHpK6gWVXL2Rjt0R5TdMRwKg/config
\
           TARGETS=rust debugkernel cpupower headers kernel kselftest modules

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