[LLDB] Fix warnings in DIL. (#134778)
This fixes 3 warnings from compiling the DILParser:
DILParser.h:53:12: warning: returning address of local temporary object
[-Wreturn-stack-address]
DILParser.h:119:8: warning: private field 'm_fragile_ivar' is not used
[-Wunused-private-field]
DILParser.h:120:8: warning: private field 'm_check_ptr_vs_member' is not
used [-Wunused-private-field]
