[Clang] [OMPIRBuilder] Prevent Null Pointer Dereference in OpenMP IR Builder (#115506)

This commit addresses Static Analyzer issues related to potential null
dereference by replacing dyn_cast<> with cast<> in OMPIRBuilder.cpp to
ensure that ArgStructType is not null before it is used, improving the
stability and reliability of the code.

Author: smanna12

llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp

@@ -6962,8 +6962,7 @@ static Function *emitTargetTaskProxyFunction(OpenMPIRBuilder &OMPBuilder,
     assert(ArgStructAlloca &&
            "Unable to find the alloca instruction corresponding to arguments "
            "for extracted function");
-    auto *ArgStructType =
-        dyn_cast<StructType>(ArgStructAlloca->getAllocatedType());
+    auto *ArgStructType = cast<StructType>(ArgStructAlloca->getAllocatedType());
 
     AllocaInst *NewArgStructAlloca =
         Builder.CreateAlloca(ArgStructType, nullptr, "structArg");