Exclude version symbols for static libomp

We use symbol versioning for GNU-compatibility but libgomp has versioned symbols
only in the shared library but not in the static.
Moreover, version symbols in the static library can cause an error at link time.

Patch by Olga Malysheva

Differential Revision: https://reviews.llvm.org/D36225


git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@309877 91177308-0d34-0410-b5e6-96231b3b80d8