Reland [lldb] Fix TestThreadStepOut.py after "Flush local value map on every instruction"

The original patch got reverted as a dependency of cf1c774d .
That patch got relanded so it's also necessary to reland this patch.

Original summary:

After cf1c774d, Clang seems to generate code
that is more similar to icc/Clang, so we can use the same line numbers for
all compilers in this test.