[lldb] Fix windows build failure due to undefined macro

This should fix a build failure on Windows caused by the macro
__PRETTY_FUNCTION__ not being defined.

https://lab.llvm.org/buildbot/#/builders/83/builds/10836

https://reviews.llvm.org/D107585



Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>