Add a build setting to disable Swift stdlib binary thinning.

This toggles a mode in support tooling to skip the "lipo" phase, instead going straight to a copy + set 0o755 operation.

PiperOrigin-RevId: 854618465
(cherry picked from commit 9e5d844)

Author: nglevin

apple/build_settings/build_settings.bzl

@@ -23,6 +23,13 @@ build_flags = {
         doc = """
 Configuration for enabling XCFramework import rules use the xcframework_processor_tool to
 parse the XCFramework bundle Info.plist file. See apple/internal/apple_xcframework_import.bzl
+""",
+        default = False,
+    ),
+    "disable_swift_stdlib_binary_thinning": struct(
+        doc = """
+Disables binary thinning for Swift stdlib binaries, matching the most recent Xcode handling for
+Swift support dylibs.
 """,
         default = False,
     ),

apple/internal/partials/swift_dylibs.bzl

@@ -97,6 +97,9 @@ def _swift_dylib_action(
     if strip_bitcode:
         swift_stdlib_tool_args.add("--strip_bitcode")
 
+    if platform_prerequisites.build_settings.disable_swift_stdlib_binary_thinning:
+        swift_stdlib_tool_args.add("--disable_binary_thinning")
+
     apple_support.run(
         actions = actions,
         apple_fragment = platform_prerequisites.apple_fragment,