Allow disabling -dead_strip in opt builds

Fixes #308

Author: keith

crosstool/cc_toolchain_config.bzl

@@ -1059,11 +1059,6 @@ please file an issue at https://github.com/bazelbuild/apple_support/issues/new
                     ),
                 ],
             ),
-            flag_set(
-                actions = _DYNAMIC_LINK_ACTIONS,
-                flag_groups = [flag_group(flags = ["-dead_strip"])],
-                with_features = [with_feature_set(features = ["opt"])],
-            ),
         ],
     )
 
@@ -2077,6 +2072,18 @@ please file an issue at https://github.com/bazelbuild/apple_support/issues/new
         ],
     )
 
+    dead_strip_opt_feature = feature(
+        name = "dead_strip_opt",
+        enabled = True,
+        flag_sets = [
+            flag_set(
+                actions = _DYNAMIC_LINK_ACTIONS,
+                flag_groups = [flag_group(flags = ["-dead_strip"])],
+                with_features = [with_feature_set(features = ["opt"])],
+            ),
+        ],
+    )
+
     oso_prefix_feature = feature(
         name = "oso_prefix_is_pwd",
         enabled = True,
@@ -2582,6 +2589,7 @@ please file an issue at https://github.com/bazelbuild/apple_support/issues/new
         default_link_flags_feature,
         no_deduplicate_feature,
         dead_strip_feature,
+        dead_strip_opt_feature,
         apply_implicit_frameworks_feature,
         link_cocoa_feature,
         apply_simulator_compiler_flags_feature,

test/linking_tests.bzl

@@ -13,6 +13,15 @@ opt_test = make_action_command_line_test_rule(
     },
 )
 
+opt_dead_strip_disabled_test = make_action_command_line_test_rule(
+    config_settings = {
+        "//command_line_option:compilation_mode": "opt",
+        "//command_line_option:features": [
+            "-dead_strip_opt",
+        ],
+    },
+)
+
 dead_strip_requested_test = make_action_command_line_test_rule(
     config_settings = {
         "//command_line_option:compilation_mode": "fastbuild",
@@ -76,6 +85,23 @@ def linking_test_suite(name):
         target_under_test = "//test/test_data:macos_binary",
     )
 
+    opt_dead_strip_disabled_test(
+        name = "{}_opt_dead_strip_disabled_test".format(name),
+        tags = [name],
+        expected_argv = [
+            "-Xlinker",
+            "-objc_abi_version",
+            "-Xlinker",
+            "2",
+            "-ObjC",
+        ],
+        not_expected_argv = [
+            "-dead_strip",
+        ],
+        mnemonic = "ObjcLink",
+        target_under_test = "//test/test_data:macos_binary",
+    )
+
     dead_strip_requested_test(
         name = "{}_dead_strip_requested_test".format(name),
         tags = [name],