Restore StubSecretArg from stack

Issue #100301

Co-authored-by: Jakob Botsch Nielsen <Jakob.botsch.nielsen@gmail.com>

Author: t-mustafin

src/coreclr/jit/lower.cpp

@@ -5610,8 +5610,11 @@ void Lowering::InsertPInvokeMethodProlog()
     call->gtArgs.PushBack(comp, frameAddrArg);
 // for x86/arm32 don't pass the secretArg.
 #if !defined(TARGET_X86) && !defined(TARGET_ARM)
+    if (comp->lvaStubArgumentVar == BAD_VAR_NUM)
+        comp->lvaStubArgumentVar = comp->lvaInlinedPInvokeFrameVar;
+
     NewCallArg stubParamArg =
-        NewCallArg::Primitive(PhysReg(REG_SECRET_STUB_PARAM)).WellKnown(WellKnownArg::SecretStubParam);
+        NewCallArg::Primitive(comp->gtNewLclvNode(comp->lvaStubArgumentVar, TYP_I_IMPL)).WellKnown(WellKnownArg::SecretStubParam);
     call->gtArgs.PushBack(comp, stubParamArg);
 #endif