Avoid unevaluated implicit private (#92055)

For every variable used under `#pragma omp task` directive
(`DeclRefExpr`) an ImplicitPrivateVariable is created in the AST, if
`private` or `shared` clauses are not present. If the variable has the
property of `non_odr_use_unevaluated` e.g. for statements which use
`sizeof( i )` `i` will have `non_odr_use_unevaluated` . In such cases
CodeGen was asserting by avoiding emitting of LLVM IR for such
variables. To prevent this assertion this checkin avoids adding the
ImplicitPrivateVariable for variables with `non_odr_use_unevaluated`.

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Authored-by: Sunil Kuravinakop <kuravina@pe28vega.us.cray.com>