Collect the embedded pymupdf_layout and pymupdf4llm sources by walking the
unpacked release tarballs; pipcl.git_items() runs `git ls-files` and fails
outside a git checkout.

--- a/setup.py
+++ b/setup.py
@@ -892,7 +892,7 @@
         ret.append( (f'{g_root}/src/build/{sharedlibrary_leaf_tgif}', to_dir) )
         ret.append( (f'{g_root}/src/build/{sharedlibrary_leaf_features}', to_dir) )
 
-        for p in pipcl.git_items(f'{PYMUPDF_SETUP_PATH_LAYOUT}/source/layout'):
+        for p in _tree_items(f'{PYMUPDF_SETUP_PATH_LAYOUT}/source/layout'):
             ret.append( (f'{PYMUPDF_SETUP_PATH_LAYOUT}/source/layout/{p}', f'{to_dir}layout/{p}'))
         
         build_py = ''
@@ -906,7 +906,7 @@
     if PYMUPDF_SETUP_PATH_4LLM:
         # 4llm
         pipcl.run(f'git config --global --add safe.directory {PYMUPDF_SETUP_PATH_4LLM}', check=0)
-        for p in pipcl.git_items(f'{PYMUPDF_SETUP_PATH_4LLM}/src'):
+        for p in _tree_items(f'{PYMUPDF_SETUP_PATH_4LLM}/src'):
             ret.append((f'{PYMUPDF_SETUP_PATH_4LLM}/src/{p}', f'pymupdf4llm/{p}'))
         ret.append((
                 textwrap.dedent(f'''
@@ -925,6 +925,19 @@
     return ret
 
 
+def _tree_items(directory):
+    '''
+    Like pipcl.git_items(), but also works on a release tarball that is not a
+    git checkout.
+    '''
+    ret = []
+    for dirpath, dirnames, filenames in os.walk(directory):
+        dirnames[:] = sorted(d for d in dirnames if d != '__pycache__')
+        for filename in sorted(filenames):
+            ret.append(os.path.relpath(os.path.join(dirpath, filename), directory))
+    return ret
+
+
 def env_add(env, name, value, sep=' ', prepend=False, verbose=False):
     '''
     Appends/prepends `<value>` to `env[name]`.