Debugger: Pinned LLDB tooltip stepping with out-of-source builds

Previously it "released" on step as the scope paths from the code
model and the debugger report "differed" ("a/b/../c" vs "a/c")

Change-Id: Ida094581cfaa53b00f9186495870854ca431f041
Reviewed-by: Christian Stenger <christian.stenger@theqtcompany.com>