[llvm] [llvm-readobj] enable demangle option for the xcoff object file (PR #78455)

[zhijian lin via llvm-commits]

diggerlin wrote:

the buildkite/g fail look not related to the patch , it fail at 

 FAILED: tools/flang/test/CMakeFiles/check-flang 
_bk;t=1709146033248 cmd.exe /C "cd /D C:\ws\src\build\tools\flang\test && C:\Python39\python.exe C:/ws/src/build/./bin/llvm-lit.py -v --xunit-xml-output C:/ws/src/build/test-results.xml --timeout=1200 --time-tests --param flang_site_config=C:/ws/src/build/tools/flang/test/lit.site.cfg.py C:/ws/src/build/tools/flang/test"
_bk;t=1709146033248 ninja: build stopped: subcommand failed.

https://github.com/llvm/llvm-project/pull/78455