Update gen.py aoti_fm install dir (pytorch#125087)

Summary: make it consistent with all the other install dir

Test Plan: Sandcastle

Differential Revision: D56660301

Pull Request resolved: pytorch#125087
Approved by: https://github.com/frank-wei

torchgen/gen.py

@@ -2710,6 +2710,12 @@ def main() -> None:
         help="output directory",
         default="build/aten/src/ATen",
     )
+    parser.add_argument(
+        "--aoti-install-dir",
+        "--aoti_install_dir",
+        help="output directory for AOTInductor shim",
+        default="torch/csrc/inductor/aoti_torch/generated",
+    )
     parser.add_argument(
         "--rocm",
         action="store_true",
@@ -2830,15 +2836,15 @@ def main() -> None:
     pathlib.Path(core_install_dir).mkdir(parents=True, exist_ok=True)
     ops_install_dir = f"{options.install_dir}/ops"
     pathlib.Path(ops_install_dir).mkdir(parents=True, exist_ok=True)
+    aoti_install_dir = f"{options.aoti_install_dir}"
+    pathlib.Path(aoti_install_dir).mkdir(parents=True, exist_ok=True)
 
     core_fm = make_file_manager(options=options, install_dir=core_install_dir)
     cpu_fm = make_file_manager(options=options)
     cpu_vec_fm = make_file_manager(options=options)
     cuda_fm = make_file_manager(options=options)
     ops_fm = make_file_manager(options=options, install_dir=ops_install_dir)
-    aoti_fm = make_file_manager(
-        options=options, install_dir="torch/csrc/inductor/aoti_torch/generated"
-    )
+    aoti_fm = make_file_manager(options=options, install_dir=aoti_install_dir)
 
     # Only a limited set of dispatch keys get CPUFunctions.h headers generated
     # for them; this is the set