[DebugInfo] Only create concrete DIEs of concrete functions

At the begining of the module we can iterate through the functions to
see which SPs should have concrete DIEs. Then when we need to reference
a DIE for a SP we can decide if it's ok to create a concrete DIE or not.

Fixes
 * https://bugs.llvm.org/show_bug.cgi?id=52159
 * https://bugs.llvm.org/show_bug.cgi?id=30637

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D112337