fatal error: 'libxml/parser.h' file not found

解决办法：

  s.pod_target_xcconfig = {
    'CLANG_CXX_LANGUAGE_STANDARD' => 'gnu++11',
    'CLANG_CXX_LIBRARY' => 'libc++',
    'HEADER_SEARCH_PATHS' => '$(SDKROOT)/usr/include/libxml2'
  }

参考：https://github.com/SVGKit/SVGKit/blob/3.x/SVGKit.podspec