[lli] Mimic default LLJIT logic with explicit --jit-linker option (llvm#76964)

Forcing the JITLinker to the default configuration shouldn't affect the
configuration of the JIT. Since it's implemented by setting the
ObjectLinkingLayerCreator, it did have side-effects though. In
particular, we skipped the Code- and RelocationModel setting in
`LLJITBuilderState::prepareForConstruction()`.

Author: weliveindetail

llvm/tools/lli/lli.cpp

@@ -965,9 +965,12 @@ int runOrcJIT(const char *ProgName) {
     EPC = ExitOnErr(orc::SelfExecutorProcessControl::Create(
         std::make_shared<orc::SymbolStringPool>()));
 
-    Builder.setObjectLinkingLayerCreator([&EPC, &P](orc::ExecutionSession &ES,
-                                                    const Triple &TT) {
-      auto L = std::make_unique<orc::ObjectLinkingLayer>(ES, EPC->getMemMgr());
+    Builder.getJITTargetMachineBuilder()
+        ->setRelocationModel(Reloc::PIC_)
+        .setCodeModel(CodeModel::Small);
+    Builder.setObjectLinkingLayerCreator([&P](orc::ExecutionSession &ES,
+                                              const Triple &TT) {
+      auto L = std::make_unique<orc::ObjectLinkingLayer>(ES);
       if (P != LLJITPlatform::ExecutorNative)
         L->addPlugin(std::make_unique<orc::EHFrameRegistrationPlugin>(
             ES, ExitOnErr(orc::EPCEHFrameRegistrar::Create(ES))));