gitlab: just use plain --cc=clang for custom runner build

I think this was because older Ubuntu's didn't alias clang to whatever
the latest version was. They do now so lets use that and not break.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230124180127.1881110-4-alex.bennee@linaro.org>

.gitlab-ci.d/custom-runners/ubuntu-22.04-aarch64.yml

@@ -81,7 +81,7 @@ ubuntu-22.04-aarch64-clang:
  script:
  - mkdir build
  - cd build
- - ../configure --disable-libssh --cc=clang-10 --cxx=clang++-10 --enable-sanitizers
+ - ../configure --disable-libssh --cc=clang --cxx=clang++ --enable-sanitizers
    || { cat config.log meson-logs/meson-log.txt; exit 1; }
  - make --output-sync -j`nproc --ignore=40`
  - make --output-sync -j`nproc --ignore=40` check