Linux: Dynamically load libudev.

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)
 
 config("libusb_config") {
   include_dirs = [
     "src/libusb",
   ]
 }
 
 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",
     "src/libusb/libusb.h",
     "src/libusb/libusbi.h",
     "src/libusb/os/darwin_usb.c",
     "src/libusb/os/darwin_usb.h",
-    "src/libusb/os/linux_udev.c",
+    "src/libusb/os/linux_udev.cc",
     "src/libusb/os/linux_usbfs.c",
     "src/libusb/os/linux_usbfs.h",
     "src/libusb/os/poll_posix.c",
     "src/libusb/os/poll_posix.h",
     "src/libusb/os/poll_windows.c",
     "src/libusb/os/poll_windows.h",
     "src/libusb/os/threads_posix.c",
     "src/libusb/os/threads_posix.h",
     "src/libusb/os/threads_windows.c",
     "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/libusb/strerror.c",
     "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",
   ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
 
   public_configs = [ ":libusb_config" ]
 
   if (is_posix) {
@@ skipping 17 matching lines @@
     ]
   }
 
   if (is_linux) {
     defines += [
       "HAVE_LIBUDEV=1",
       "OS_LINUX=1",
       "USE_UDEV=1",
       "_GNU_SOURCE=1",
     ]
-    configs += [ "//build/config/linux:udev" ]
+    deps += [ "//build/config/linux:udev" ]
   } else {
     sources -= [
-      "src/libusb/os/linux_udev.c",
+      "src/libusb/os/linux_udev.cc",
       "src/libusb/os/linux_usbfs.c",
       "src/libusb/os/linux_usbfs.h",
     ]
   }
 
   if (is_win) {
     include_dirs += [ "src/msvc" ]
     sources -= [
       "src/libusb/os/poll_posix.c",
       "src/libusb/os/threads_posix.c",
     ]
   } else {
     include_dirs += [ "src" ]
     sources -= [
       "src/libusb/os/poll_windows.c",
       "src/libusb/os/poll_windows.h",
       "src/libusb/os/threads_windows.c",
       "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",
     ]
   }
 }