[Frontend][OpenMP] Add deduction guide for ConstructCompositionT

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Differential Revision: https://phabricator.intern.facebook.com/D60251099

Author: kparzysz

llvm/include/llvm/Frontend/OpenMP/ConstructCompositionT.h

@@ -81,6 +81,10 @@ template <typename ClauseType> struct ConstructCompositionT {
   std::unordered_map<llvm::omp::Clause, ClauseSet> clauseSets;
 };
 
+template <typename ClauseTy>
+ConstructCompositionT(uint32_t, llvm::ArrayRef<DirectiveWithClauses<ClauseTy>>)
+    -> ConstructCompositionT<ClauseTy>;
+
 template <typename C>
 ConstructCompositionT<C>::ConstructCompositionT(
     uint32_t version, llvm::ArrayRef<DirectiveWithClauses<C>> leafs)