Rollback accidental change to CGO.RelocationModel (#2499)

src/ngraph/codegen/compiler.cpp

@@ -239,7 +239,7 @@ void codegen::CompilerCore::initialize()
     // CodeGen options
     auto& CGO = m_compiler->getInvocation().getCodeGenOpts();
     CGO.OptimizationLevel = 3;
-    CGO.RelocationModel = llvm::Reloc::Model::Static;
+    CGO.RelocationModel = "static";
     // CGO.CodeModel = "medium";
     CGO.ThreadModel = "posix";
     CGO.FloatABI = "hard";