Add -no_deduplicate for darwin dbg/fastbuild

The -no_deduplicate linker flag saves some time for debug builds at the
cost of binary size. In testing envoy the difference was 50s -> 9s to
link a debug build with this flag enabled. This change enables it as a
separate feature so it can be opted out of by users if needed, and
leaves the default for opt to get this optimization for release builds.

Fixes https://github.com/bazelbuild/bazel/issues/10910

Closes #15635.

PiperOrigin-RevId: 475592901
Change-Id: I8746ffa9492ebffed52dd680c3dd4e0283772447

tools/osx/crosstool/cc_toolchain_config.bzl

diff --git a/tools/osx/crosstool/cc_toolchain_config.bzl b/tools/osx/crosstool/cc_toolchain_config.bzl
index 2574ba8..73187d2 100644
--- a/tools/osx/crosstool/cc_toolchain_config.bzl
+++ b/tools/osx/crosstool/cc_toolchain_config.bzl
@@ -1161,6 +1161,28 @@
             ],
         )
 
+    no_deduplicate_feature = feature(
+        name = "no_deduplicate",
+        enabled = True,
+        flag_sets = [
+            flag_set(
+                actions = all_link_actions +
+                          ["objc-executable", "objc++-executable"],
+                flag_groups = [
+                    flag_group(
+                        flags = [
+                            "-Xlinker",
+                            "-no_deduplicate",
+                        ],
+                    ),
+                ],
+                with_features = [
+                    with_feature_set(not_features = ["opt"]),
+                ],
+            ),
+        ],
+    )
+
     output_execpath_flags_feature = feature(
         name = "output_execpath_flags",
         flag_sets = [
@@ -2748,6 +2770,7 @@
             relative_ast_path_feature,
             user_link_flags_feature,
             default_link_flags_feature,
+            no_deduplicate_feature,
             dead_strip_feature,
             cpp_linker_flags_feature,
             apply_implicit_frameworks_feature,
@@ -2829,6 +2852,7 @@
             relative_ast_path_feature,
             user_link_flags_feature,
             default_link_flags_feature,
+            no_deduplicate_feature,
             dead_strip_feature,
             cpp_linker_flags_feature,
             apply_implicit_frameworks_feature,