Build fixes for fnl/musl

build/config/fnl/BUILD.gn

 # Copyright 2015 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("//build/config/linux/pkg_config.gni")
 import("//build/config/features.gni")
 import("//build/config/sysroot.gni")
 import("//build/config/ui.gni")
 
 config("sdk") {
   if (sysroot != "") {
     cflags = [ "--sysroot=" + sysroot ]
     ldflags = [ "--sysroot=" + sysroot ]
 
     # Need to get some linker flags out of the sysroot.
     ldflags += [ exec_script("../linux/sysroot_ld_path.py",
                              [
                                rebase_path("//build/linux/sysroot_ld_path.sh",
                                            root_build_dir),
                                sysroot,
                              ],
                              "value") ]
   }
 
-  defines = []
+  defines = [ "FNL_MUSL" ]
 
   if (use_ozone) {
     defines += [ "MESA_EGL_NO_X11_HEADERS" ]
   }
 }
 
 config("fontconfig") {
   libs = [ "fontconfig" ]
 }
 
 pkg_config("freetype2") {
   packages = [ "freetype2" ]
 }
 
 if (use_evdev_gestures) {
   pkg_config("libevdev-cros") {
     packages = [ "libevdev-cros" ]
   }
 
   pkg_config("libgestures") {
     packages = [ "libgestures" ]
   }
 }