Use a parameter file when linking Swift libraries when the host machine

is macOS.

This is to prevent the linking failures if a `swift_library` target has
too many files that can cause its linking args to become longer than the
system's command length limits. This does not change the behavior when
building on Linux yet, since `ar` does not support passing arguments
using a parameter file.

swift/internal/linking.bzl

@@ -22,6 +22,18 @@ load(
 )
 load(":derived_files.bzl", "derived_files")
 
+def _is_apple_platform_toolchain(swift_toolchain):
+    """Returns `True` if the given Swift toolchain is for Apple platforms.
+
+    Args:
+        swift_toolchain: A `SwiftToolchainInfo` provider representing a Swift
+            compiler toolchain.
+
+    Returns:
+        `True` if the given Swift toolchain is for Apple platforms.
+    """
+    return swift_toolchain.system_name == "darwin"
+
 def _register_static_library_link_action(
         actions,
         cc_feature_configuration,
@@ -58,7 +70,17 @@ def _register_static_library_link_action(
     )
     args = actions.args()
     args.add_all(command_line)
-    args.add_all(objects)
+    filelist_args = actions.args()
+
+    # Use a parameter file when building on macOS. `ar` on Linux does not
+    # support this yet, so we're passing parameters to the command line as is.
+    if _is_apple_platform_toolchain(swift_toolchain):
+        args.add("-filelist")
+        filelist_args.set_param_file_format("multiline")
+        filelist_args.use_param_file("%s", use_always = True)
+        filelist_args.add_all(objects)
+    else:
+        args.add_all(objects)
 
     env = cc_common.get_environment_variables(
         action_name = CPP_LINK_STATIC_LIBRARY_ACTION_NAME,
@@ -73,7 +95,7 @@ def _register_static_library_link_action(
     execution_requirements = {req: "1" for req in execution_requirements_list}
 
     actions.run(
-        arguments = [args],
+        arguments = [args, filelist_args],
         env = env,
         executable = archiver_path,
         execution_requirements = execution_requirements,