Use default value on empty llvm_code_path (#72758)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/72758
Bug: FLAGS_output_llvm option was introduced recently to specify LLVM assembly code file. Without previously default value, now the llvm code is not being saved to a file if asmfile input is not specified and is resulting in making the compiled output unusable.
Fix: Use default value if output_llvm/asmfile input is not specified.
Test Plan: Verified that output is saved to deafult .ll file path
Reviewed By: IvanKobzarev
Differential Revision: D34189107
fbshipit-source-id: ee51e8c17de92d3045690ca871fb9569fc3164d6
(cherry picked from commit 46352d446b3e9d7df0eddf0a29790de6f7757d26)
