Un-nest configs in GN files.

third_party/libxslt/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.
 
 config("libxslt_config") {
   defines = [ "LIBXSLT_STATIC" ]
   include_dirs = [ "." ]
 }
 
+config("libxslt_warnings") {
+  if (is_clang) {
+    cflags = [
+      # libxslt stores a char[3] in a `const unsigned char*`.
+      "-Wno-pointer-sign",
+
+      # xsltDefaultRegion and xsltCalibrateTimestamps are only
+      # used with certain preprocessor defines set.
+      "-Wno-unused-function",
+    ]
+  }
+}
+
 static_library("libxslt") {
   sources = [
     "libxslt/attributes.c",
     "libxslt/attributes.h",
     "libxslt/attrvt.c",
     "libxslt/documents.c",
     "libxslt/documents.h",
     "libxslt/extensions.c",
     "libxslt/extensions.h",
     "libxslt/extra.c",
@@ skipping 32 matching lines @@
     "libxslt/xsltlocale.c",
     "libxslt/xsltlocale.h",
     "libxslt/xsltutils.c",
     "libxslt/xsltutils.h",
     "libxslt/xsltwin32config.h",
     "linux/config.h",
     "mac/config.h",
     "win32/config.h",
   ]
 
-  config("libxslt_warnings") {
-    if (is_clang) {
-      cflags = [
-        # libxslt stores a char[3] in a `const unsigned char*`.
-        "-Wno-pointer-sign",
-
-        # xsltDefaultRegion and xsltCalibrateTimestamps are only
-        # used with certain preprocessor defines set.
-        "-Wno-unused-function",
-      ]
-    }
-  }
   configs -= [ "//build/config/compiler:chromium_code" ]
-  configs += [ "//build/config/compiler:no_chromium_code" ]
-  configs += [ ":libxslt_warnings" ]
+  configs += [
+    ":libxslt_warnings",
+    "//build/config/compiler:no_chromium_code",
+  ]
   public_configs = [ ":libxslt_config" ]
 
   cflags = []
   if (is_linux || is_android) {
     include_dirs = [ "linux" ]
   } else if (is_win) {
     include_dirs = [ "win32" ]
     cflags += [ "/wd4267" ]  # size_t to int.
   } else if (is_mac) {
     include_dirs = [ "mac" ]
   }
 
   deps = [
     "//third_party/libxml",
   ]
 }