Calling ParseCommandLineOptions should only be called from main as the
CommandLine setup code isn't thread-safe. As BackendUtil is part of the
generic Clang FrontendAction logic, a process which has several threads executing
Clang FrontendActions will randomly crash in the unsafe setup code.
This patch avoids calling the function unless either the debug-pass option or
limit-float-precision option is set. Without these two options set the
ParseCommandLineOptions call doesn't do anything beside parsing
the command line clang which doesn't set any options.
See also D99652 where LLDB received a workaround for this crash.