usbmuxd: Pass path to libusb headers to CMake

CMake fails to find this info on it's own.

Fixes Homebrew/homebrew#7293.

Formula/usbmuxd.rb

@@ -8,12 +8,26 @@ class Usbmuxd < Formula
   head 'http://cgit.sukimashita.com/usbmuxd.git'
 
   depends_on 'cmake' => :build
+  depends_on 'pkg-config' => :build
+
   depends_on 'libusb'
   depends_on 'libplist'
 
   def install
+    libusb = Formula.factory 'libusb'
     inreplace 'Modules/VersionTag.cmake', '"sh"', '"bash"'
-    system "cmake #{std_cmake_parameters} -DLIB_SUFFIX='' ."
-    system "make install"
+
+    # The CMake scripts responsible for locating libusb headers are broken. So,
+    # we explicitly point the build script at the proper directory.
+    args = std_cmake_parameters.split.concat %W[
+      -DLIB_SUFFIX=''
+      -DUSB_INCLUDE_DIR='#{libusb.include.children.first}'
+    ]
+
+    mkdir 'build'
+    chdir 'build' do
+      system 'cmake', '..', *args
+      system 'make install'
+    end
   end
 end