Copy module file instead of symlinking.

This is primary to work around bazelbuild/bazel#20886,
but also helps on Windows if symbolic links aren’t supported.

elisp/BUILD

@@ -481,6 +481,14 @@ elisp_binary(
     visibility = ["//visibility:public"],
 )
 
+py_binary(
+    name = "copy_file",
+    srcs = ["copy_file.py"],
+    python_version = "PY3",
+    srcs_version = "PY3",
+    visibility = [":__pkg__"],
+)
+
 cc_defaults(
     name = "launcher_defaults",
     copts = LAUNCHER_COPTS,

elisp/copy_file.py

@@ -0,0 +1,29 @@
+# Copyright 2024 Philipp Stephani
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import argparse
+import pathlib
+import shutil
+
+
+def _main() -> None:
+    parser = argparse.ArgumentParser(allow_abbrev=False)
+    parser.add_argument('source', type=pathlib.Path)
+    parser.add_argument('dest', type=pathlib.Path)
+    args = parser.parse_args()
+    shutil.copyfile(args.source, args.dest)
+
+
+if __name__ == '__main__':
+    _main()

elisp/defs.bzl

@@ -527,10 +527,13 @@ def _elisp_cc_module_impl(ctx):
         lib = out.library_to_link.dynamic_library
     else:
         lib = ctx.actions.declare_file(filename)
-        ctx.actions.symlink(
-            output = lib,
-            target_file = out.library_to_link.dynamic_library,
-            progress_message = "Creating symbolic link " + lib.short_path,
+        ctx.actions.run(
+            executable = ctx.executable._copy_file,
+            arguments = [ctx.actions.args().add("--").add(out.library_to_link.dynamic_library).add(lib)],
+            inputs = [out.library_to_link.dynamic_library],
+            outputs = [lib],
+            mnemonic = "Copy",
+            progress_message = "Copying %{input} to %{output}",
         )
 
     # Replicate some implementation details of cc_binary to make coverage work,
@@ -645,6 +648,11 @@ C/C++ compiler.  See the [corresponding attribute for
             default = Label("//elisp:module_config"),
             providers = [CcDefaultInfo, ModuleConfigInfo],
         ),
+        "_copy_file": attr.label(
+            default = Label("//elisp:copy_file"),
+            executable = True,
+            cfg = "exec",
+        ),
     },
     provides = [EmacsLispInfo],
     fragments = ["cpp"],