According to the comment removed in commit fae0295a799499268caca9c385ac4d7061543980, clang was only used to avoid OOM. Using GCC today should be fine.
(Meta note: The task can maybe even be removed in a few years, see #35230#issue-4397029749)
If OOM is an issue, or even if there is no issue, maybe DEBUG=1 should be removed, because the ci/test/00_setup_env_native_alpine_musl.sh config is already checking DEBUG=1 with GCC.