[lldbsuite] Fix the mac version decorator to work on non-mac platforms
Summary: On non-mac platforms, mac_ver returns an empty string which when converted to LooseVersion has no "version" property. This causes a failure when the decorator executes. Instead, check whether the value returned from mac_ver is an empty string and avoid the LooseVersion comparison.
Reviewers: labath, davide, asmith, shafik, jingham
Reviewed By: jingham
Subscribers: jingham, lldb-commits
Differential Revision: https://reviews.llvm.org/D53208
llvm-svn: 344623