Unpack llvm-project v20 has "Cannot create symlink" prolem on Windows

[shenxianpeng]

Run # ignore failure on v21 on windows
tar: llvm-project-21.1.0.src/llvm/utils/mlgo-utils/combine_training_corpus.py: Cannot create symlink to 'mlgo/corpus/combine_training_corpus.py': No such file or directory
tar: llvm-project-21.1.0.src/llvm/utils/mlgo-utils/extract_ir.py: Cannot create symlink to 'mlgo/corpus/extract_ir.py': No such file or directory
tar: llvm-project-21.1.0.src/llvm/utils/mlgo-utils/make_corpus.py: Cannot create symlink to 'mlgo/corpus/make_corpus.py': No such file or directory
tar: Exiting with failure status due to previous errors

[shenxianpeng]

Right now, I just add || true to ignore the failure. Maybe it would be fixed in the future release package from the llvm-project.