Explicitly pass -Wno-unused-function to the targets that need it.

third_party/sqlite/BUILD.gn

 # Copyright (c) 2013 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.
 
 declare_args() {
   # Controls whether the build should uses the version of sqlite3 library
   # shipped with the system (currently only supported on iOS) or the one
   # shipped with Chromium source.
   use_system_sqlite = is_ios
 }
@@ skipping 39 matching lines @@
     }
     if (is_linux || is_android) {
       defines += [
         # Linux provides fdatasync(), a faster equivalent of fsync().
         "fdatasync=fdatasync",
       ]
     }
 
     include_dirs = [ "amalgamation" ]
 
+    config("sqlite_warnings") {
+      cflags = []
+      if (is_clang) {
+        # sqlite contains a few functions that are unused, at least on
+        # Windows with Chromium's sqlite patches applied
+        # (interiorCursorEOF fts3EvalDeferredPhrase
+        # fts3EvalSelectDeferred sqlite3Fts3InitHashTable
+        # sqlite3Fts3InitTok).
+        cflags += [ "-Wno-unused-function" ]
+      }
+      if (is_linux) {
+        cflags += [
+          # SQLite doesn"t believe in compiler warnings,
+          # preferring testing.
+          #   http://www.sqlite.org/faq.html#q17
+          "-Wno-int-to-pointer-cast",
+          "-Wno-pointer-to-int-cast",
+        ]
+      }
+    }
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
+    configs += [ ":sqlite_warnings" ]
 
     if (is_linux) {
-      cflags += [
-        # SQLite doesn"t believe in compiler warnings,
-        # preferring testing.
-        #   http://www.sqlite.org/faq.html#q17
-        "-Wno-int-to-pointer-cast",
-        "-Wno-pointer-to-int-cast",
-      ]
       libs = [ "dl" ]
     } else if (is_mac || is_ios) {
       libs = [ "CoreFoundation.framework" ]
     } else if (is_android) {
       defines += [
         "SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT=1048576",
         "SQLITE_DEFAULT_AUTOVACUUM=1",
         "SQLITE_TEMP_STORE=3",
         "SQLITE_ENABLE_FTS3_BACKWARDS",
         "DSQLITE_DEFAULT_FILE_FORMAT=4",
@@ skipping 69 matching lines @@
         "//third_party/icu",
       ]
       if (is_clang) {
         # src/ext/icu/icu.c uses assert(!"string") which causes warnings about
         # conversion from string literal to bool.
         configs -= [ "//build/config/clang:extra_warnings" ]
       }
     }
   }
 }