[OPENMP] Fix compiler crash during data-sharing attributes analysis.

If a global variable is marked as private in OpenMP construct and then is used in of the private clauses of the same construct, it might cause compiler crash because of incorrect capturing.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@243964 91177308-0d34-0410-b5e6-96231b3b80d8