hooks: add hook for fvcore.nn

Add hook for `fvcore.nn` to collect its source .py files for
torchscript/JIT.

Add a basic import test that demonstrates the need for that.

news/676.new.10.rst

@@ -0,0 +1,2 @@
+Add hook for ``fvcore.nn`` to collect its source .py files for
+TorchScript/JIT.

src/_pyinstaller_hooks_contrib/hooks/stdhooks/hook-fvcore.nn.py

@@ -0,0 +1,14 @@
+# ------------------------------------------------------------------
+# Copyright (c) 2023 PyInstaller Development Team.
+#
+# This file is distributed under the terms of the GNU General Public
+# License (version 2.0 or later).
+#
+# The full license is available in LICENSE.GPL.txt, distributed with
+# this software.
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+# ------------------------------------------------------------------
+
+# Collect source .py files for JIT/torchscript. Requires PyInstaller >= 5.3, no-op in older versions.
+module_collection_mode = 'pyz+py'

src/_pyinstaller_hooks_contrib/tests/test_deep_learning.py

@@ -278,3 +278,12 @@ def forward(self, x):
         print("Test X:", test_x.numpy())
         print("Predicted Y:", observed_pred.mean.numpy())
     """)
+
+
+# Basic import test for fvcore.nn, which shows that we need to collect its source.py files for TorchScript/JIT.
+@importorskip('fvcore')
+@onedir_only
+def test_fvcore(pyi_builder):
+    pyi_builder.test_source("""
+        import fvcore.nn
+    """)