Revert of Un-nest configs in GN files.

third_party/libusb/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.
 
 assert(!is_android && !is_ios)
 
 import("//build/config/features.gni")
 
 config("libusb_config") {
   include_dirs = [ "src/libusb" ]
 }
 
-config("libusb_warnings") {
-  visibility = [ ":*" ]
-  if (is_clang) {
-    # guid_eq in windows_usb.c is unused.
-    cflags = [ "-Wno-unused-function" ]
-    if (is_linux && !use_udev) {
-      cflags += [ "-Wno-pointer-sign" ]
-    }
-  }
-}
-
 static_library("libusb") {
   sources = [
     "src/config.h",
     "src/libusb/core.c",
     "src/libusb/descriptor.c",
     "src/libusb/hotplug.c",
     "src/libusb/hotplug.h",
     "src/libusb/interrupt.c",
     "src/libusb/interrupt.h",
     "src/libusb/io.c",
@@ skipping 16 matching lines @@
     "src/libusb/sync.c",
     "src/libusb/version.h",
     "src/libusb/version_nano.h",
     "src/msvc/config.h",
     "src/msvc/inttypes.h",
     "src/msvc/stdint.h",
   ]
   deps = []
   include_dirs = [ "src/libusb/os" ]
 
+  config("libusb_warnings") {
+    if (is_clang) {
+      # guid_eq in windows_usb.c is unused.
+      cflags = [ "-Wno-unused-function" ]
+      if (is_linux && !use_udev) {
+        cflags += [ "-Wno-pointer-sign" ]
+      }
+    }
+  }
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   configs += [ ":libusb_warnings" ]
 
   public_configs = [ ":libusb_config" ]
 
   if (is_posix) {
     defines = [
       "DEFAULT_VISIBILITY=",
       "HAVE_GETTIMEOFDAY=1",
@@ skipping 55 matching lines @@
       "src/libusb/os/threads_windows.h",
       "src/libusb/os/windows_common.h",
       "src/libusb/os/windows_usb.c",
       "src/libusb/os/windows_usb.h",
       "src/msvc/config.h",
       "src/msvc/inttypes.h",
       "src/msvc/stdint.h",
     ]
   }
 }