Suppress "unused-const-variable" Clang warnings.

BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//third_party/icu/config.gni")
 
 # Meta target that includes both icuuc and icui18n. Most targets want both.
 # You can depend on the individually if you need to.
 group("icu") {
   deps = [
@@ skipping 54 matching lines @@
       "-Wno-unused-function",
     ]
   }
   if (is_clang) {
     cflags += [
       "-Wno-deprecated-declarations",
       "-Wno-logical-op-parentheses",
       "-Wno-tautological-compare",
       "-Wno-switch",
       "-Wno-parentheses",
-      ]
+      # ICU generally has no unused variables, but there are a few places where
+      # this warning triggers.
+      # See https://codereview.chromium.org/1222643002/ and
+      # http://www.icu-project.org/trac/ticket/11759.
+      "-Wno-unused-const-variable",
+    ]
     if (is_win) {
       cflags += [
         # See http://bugs.icu-project.org/trac/ticket/11122
         "-Wno-inline-new-delete",
         "-Wno-implicit-exception-spec-mismatch",
         # See http://bugs.icu-project.org/trac/ticket/11757.
         "-Wno-reorder",
       ]
     }
   }
@@ skipping 400 matching lines @@
   ]
 
   configs -= [
     "//build/config/compiler:no_rtti",  # ICU uses RTTI.
     "//build/config/compiler:chromium_code",
   ]
   configs += [
     "//build/config/compiler:rtti",
     "//build/config/compiler:no_chromium_code",
   ]
+  configs += [ ":icu_code" ]

[Peter Mayo, 2015/07/06 18:01:56]

Is this an accident?  It fails my gen rebuild.

[Nico, 2015/07/06 18:03:31]

Yes, that looks like an accident (the same is added again the line below).

[Matt Giuca, 2015/07/07 03:15:53]

Oh no, looks like a rebase accident (wasn't a problem in PS1).

Looks like Nico has already fixed this in c81a1a3. Thanks, Nico.

 
   configs += [ ":icu_code" ]
   public_configs = [ ":icu_config" ]
 
   if (is_win || icu_use_data_file) {
     sources += [ "source/stubdata/stubdata.c" ]
     defines += [ "U_ICUDATAENTRY_IN_COMMON" ]
   }
 }
 
@@ skipping 59 matching lines @@
         sources = [
           "android/icudtl_dat.S",
         ]
       } else {
         assert(false, "No icu data for this platform")
       }
       defines = [ "U_HIDE_DATA_SYMBOL" ]
     }
   }
 }