Test failures on Linux aarch64

[hasufell]

On my branch release-ci we encounter test failures on Linux aarch64:

• https://github.com/stable-haskell/ghc/actions/runs/17849982701/job/50758310323

Such as:

ghc: unable to load unit `libffi-3.5.2'
*** unexpected failure for T10549(ghci)
Wrong exit code for T10549a(ghci)(expected 0 , actual 1 )
Stderr  run  ( T10549a ):
ghc: Failed to lookup symbol: __clear_cache, you might consider using --optimistic-linking

This is because:

• I created a Haskell package libffi so that we statically link libffi with ease on all platform via just depending on that package
• libffi uses a GNUC builtin __builtin___clear_cache:

  • static inline void
    ffi_clear_cache (void *start, void *end)
    {
    #if defined (__clang__) && defined (__APPLE__)
      sys_icache_invalidate (start, (char *)end - (char *)start);
    #elif defined (__GNUC__)
      __builtin___clear_cache (start, end);
    #elif defined (_WIN32)
      FlushInstructionCache(GetCurrentProcess(), start, (char*)end - (char*)start);
    #else
    #error "Missing builtin to flush instruction cache"
    #endif
    }

• apparently we never get this symbol when linking libffi into the rts and running ghci