clang when given -g on Windows produces a PDB file. For whatever reason,
the test doesn't work with that.
-gdwarf produces DWARF regardless of platform.
Fixes 803f957e87e4083f6d61c8991171eeeaf0e6bd61.
I have to check for the sc list size being changed by the call-site
search, not just that it had more than one element.
Added a test for multiple CU's with the same name in a given module,
which would have caught this mistake.
We were also doing all the work to find call sites when the found decl
and specified decl's only difference was a column, but the incoming
specification hadn't specified a column (column number == 0).
