[Executorch][Export][5/N] Remove portable lib dependency in et/export

Runtime import is forcing export to use portable lib, this diff decouples it and let's the user link the library directly with aten or portable lib

Differential Revision: [D88571674](https://our.internmc.facebook.com/intern/diff/D88571674/)

ghstack-source-id: 327669272
Pull Request resolved: #16130

Author: abhinaykukkadapu

backends/apple/coreml/TARGETS

@@ -82,6 +82,7 @@ runtime.python_library(
         "//executorch/exir/backend:partitioner",
         "//executorch/exir/backend:utils",
         "//executorch/export:lib",
+        "//executorch/runtime:runtime",  # @manual
     ],
 )
 

backends/qualcomm/recipes/TARGETS

@@ -30,6 +30,7 @@ runtime.python_library(
     deps = [
         "//caffe2:torch",
         "//executorch/export:lib",
+        "//executorch/runtime:runtime",  # @manual
         "//executorch/backends/qualcomm/partition:partition",
         "//executorch/backends/qualcomm/serialization:serialization",
         "//executorch/backends/qualcomm/utils:utils",

backends/xnnpack/recipes/TARGETS

@@ -30,6 +30,7 @@ runtime.python_library(
     deps = [
         "//caffe2:torch",
         "//executorch/export:lib",
+        "//executorch/runtime:runtime",  # @manual
         "//executorch/backends/xnnpack/quantizer:xnnpack_quantizer",
         "//executorch/backends/xnnpack/partition:xnnpack_partitioner",
         ":xnnpack_recipe_types",

backends/xnnpack/test/TARGETS

@@ -107,6 +107,7 @@ runtime.python_test(
     deps = [
        "//executorch/backends/xnnpack/recipes:xnnpack_recipes",
         "//executorch/export:lib",
+        "//executorch/runtime:runtime",  # @manual
         "//pytorch/vision:torchvision",  # @manual
         "//executorch/backends/xnnpack/test/tester:tester",
         "//executorch/examples/models:models",  # @manual

devtools/etrecord/tests/TARGETS

@@ -23,5 +23,6 @@ runtime.python_library(
         "//executorch/exir/tests:models",
         "//executorch/backends/xnnpack/partition:xnnpack_partitioner",
         "//executorch/export:lib",
+        "//executorch/runtime:runtime",  # @manual
     ],
 )

export/TARGETS

@@ -32,7 +32,6 @@ runtime.python_library(
         ":recipe",
         ":stages",
         ":types",
-        "//executorch/runtime:runtime",
         ":recipe_registry"
     ]
 )

export/export.py

@@ -629,8 +629,15 @@ def run_method(
         Raises:
             RuntimeError: If the method cannot be loaded
         """
-        # Lazy import to avoid forcing portable_lib dependency at module load time
-        from executorch.runtime import Runtime, Verification
+        # Lazy import to avoid forcing portable_lib dependency at module load time.
+        try:
+            from executorch.runtime import Runtime, Verification
+        except ModuleNotFoundError as e:
+            raise ModuleNotFoundError(
+                "executorch.runtime is not available. "
+                "In OSS: Please ensure executorch is properly installed via pip. "
+                "In fbcode: Please add //executorch/runtime:runtime to your dependencies."
+            ) from e
 
         et_runtime = Runtime.get()
         program = et_runtime.load_program(