Build issue with flang 21

[opoplawski]

There is an attempt to rebuild the stripy conda package with flang 21 here: conda-forge/stripy-feedstock#25

It's failing with errors like:

  [34/39] Linking target _stripack.cp310-win_amd64.pyd
  FAILED: [code=1104] _stripack.cp310-win_amd64.pyd
  "link"  /MACHINE:x64 /OUT:_stripack.cp310-win_amd64.pyd _stripack.cp310-win_amd64.pyd.p/meson-generated_..__stripackmodule.c.obj _stripack.cp310-win_amd64.pyd.p/meson-generated_..__stripack-f2pywrappers.f.obj _stripack.cp310-win_amd64.pyd.p/src_stripack.f90.obj _stripack.cp310-win_amd64.pyd.p/D__bld_stripy_1763207111809__h_env_lib_site-packages_numpy_f2py_src_fortranobject.c.obj "/release" "/nologo" "/OPT:REF" "/DLL" "/IMPLIB:_stripack.cp310-win_amd64.lib" "-static" "-Wl,-defaultlib:D:/bld/stripy_1763207111809/_build_env/lib/clang/21/lib/windows/clang_rt.builtins-x86_64.lib" "D:\bld\stripy_1763207111809\_h_env\libs\python310.lib" "kernel32.lib" "user32.lib" "gdi32.lib" "winspool.lib" "shell32.lib" "ole32.lib" "oleaut32.lib" "uuid.lib" "comdlg32.lib" "advapi32.lib"
  LINK : warning LNK4044: unrecognized option '/static'; ignored
  LINK : warning LNK4044: unrecognized option '/Wl,-defaultlib:D:/bld/stripy_1763207111809/_build_env/lib/clang/21/lib/windows/clang_rt.builtins-x86_64.lib'; ignored
  LINK : fatal error LNK1104: cannot open file 'flang_rt.runtime.dynamic.lib'
  [35/39] Linking target _tripack.cp310-win_amd64.pyd
  FAILED: [code=1104] _tripack.cp310-win_amd64.pyd
  "link"  /MACHINE:x64 /OUT:_tripack.cp310-win_amd64.pyd _tripack.cp310-win_amd64.pyd.p/meson-generated_..__tripackmodule.c.obj _tripack.cp310-win_amd64.pyd.p/meson-generated_..__tripack-f2pywrappers.f.obj _tripack.cp310-win_amd64.pyd.p/src_tripack.f90.obj _tripack.cp310-win_amd64.pyd.p/D__bld_stripy_1763207111809__h_env_lib_site-packages_numpy_f2py_src_fortranobject.c.obj "/release" "/nologo" "/OPT:REF" "/DLL" "/IMPLIB:_tripack.cp310-win_amd64.lib" "-static" "-Wl,-defaultlib:D:/bld/stripy_1763207111809/_build_env/lib/clang/21/lib/windows/clang_rt.builtins-x86_64.lib" "D:\bld\stripy_1763207111809\_h_env\libs\python310.lib" "kernel32.lib" "user32.lib" "gdi32.lib" "winspool.lib" "shell32.lib" "ole32.lib" "oleaut32.lib" "uuid.lib" "comdlg32.lib" "advapi32.lib"
  LINK : warning LNK4044: unrecognized option '/static'; ignored
  LINK : warning LNK4044: unrecognized option '/Wl,-defaultlib:D:/bld/stripy_1763207111809/_build_env/lib/clang/21/lib/windows/clang_rt.builtins-x86_64.lib'; ignored
  LINK : fatal error LNK1104: cannot open file 'flang_rt.runtime.dynamic.lib'
  [36/39] Compiling Fortran object _ssrfpack.cp310-win_amd64.pyd.p/src_ssrfpack.f.obj
  flang: warning: argument unused during compilation: '-Wall' [-Wunused-command-line-argument]
  ninja: build stopped: subcommand failed.
  error: subprocess-exited-with-error

Any idea what might be going on here? Thanks.