[OPENMP] Fixed codegen for lastprivate LCV in worksharing constructs.

If loop control variable in a worksharing construct is marked as lastprivate, we should copy last calculated value of private counter back to original variable.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@237879 91177308-0d34-0410-b5e6-96231b3b80d8