When selftests are built with a new enough clang, the arena selftests
opt-in to use LLVM address_space attribute annotations for arena
pointers.

These annotations are not emitted by kfunc prototype generation. This
causes compilation errors when clang sees conflicting prototypes.

Fix by opting arena selftests out of using generated kfunc prototypes.

Fixes: 770abbb5 ("bpftool: Support dumping kfunc prototypes from BTF")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202406131810.c1B8hTm8-lkp@intel.com/Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Link: https://lore.kernel.org/r/fc59a617439ceea9ad8dfbb4786843c2169496ae.1718295425.git.dxu@dxuuu.xyzSigned-off-by: Alexei Starovoitov <ast@kernel.org>