DebugInfo: Change DIBuilder to make distinct DIGlobalVariables
A long overdue change to make DIGlobalVariable distinct. Much like
DISubprogram definitions (changed in r246098), it isn't logical to
unique DIGlobalVariable definitions from two different compile units.
(Longer-term, we should also find a way to reverse the link between
GlobalVariable and DIGlobalVariable, and between DIGlobalVariable and
DICompileUnit, so that debug info to do with optimized-out globals
disappears. Admittedly it's harder than with Function/DISubprogram,
since global variables may be constant-folded and the debug info should
still describe that somehow.)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267301
91177308-0d34-0410-b5e6-
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