[MLIR] Split ExecutionEngine Initialization out of ctor into an explicit method call (#153373)

This PR introduces a mechanism to defer JIT engine initialization,
enabling registration of required symbols before global constructor
execution.

## Problem

Modules containing `gpu.module` generate global constructors (e.g.,
kernel load/unload) that execute *during* engine creation. This can
force premature symbol resolution, causing failures when:
- Symbols are registered via `mlirExecutionEngineRegisterSymbol` *after*
creation
- Global constructors exist (even if not directly using unresolved
symbols, e.g., an external function declaration)
   - GPU modules introduce mandatory binary loading logic

## Usage
```c
// Create engine without initialization
MlirExecutionEngine jit = mlirExecutionEngineCreate(...);

// Register required symbols
mlirExecutionEngineRegisterSymbol(jit, ...);

// Explicitly initialize (runs global constructors)
mlirExecutionEngineInitialize(jit);
```

---------

Co-authored-by: Mehdi Amini <[email protected]>

Author: jackalcooper

mlir/lib/Bindings/Python/ExecutionEngineModule.cpp

@@ -7,8 +7,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "mlir-c/ExecutionEngine.h"
-#include "mlir/Bindings/Python/NanobindAdaptors.h"
 #include "mlir/Bindings/Python/Nanobind.h"
+#include "mlir/Bindings/Python/NanobindAdaptors.h"
 
 namespace nb = nanobind;
 using namespace mlir;
@@ -124,6 +124,17 @@ NB_MODULE(_mlirExecutionEngine, m) {
           },
           nb::arg("name"), nb::arg("callback"),
           "Register `callback` as the runtime symbol `name`.")
+      .def(
+          "initialize",
+          [](PyExecutionEngine &executionEngine) {
+            mlirExecutionEngineInitialize(executionEngine.get());
+          },
+          "Initialize the ExecutionEngine. Global constructors specified by "
+          "`llvm.mlir.global_ctors` will be run. One common scenario is that "
+          "kernel binary compiled from `gpu.module` gets loaded during "
+          "initialization. Make sure all symbols are resolvable before "
+          "initialization by calling `raw_register_runtime` or including "
+          "shared libraries.")
       .def(
           "dump_to_object_file",
           [](PyExecutionEngine &executionEngine, const std::string &fileName) {