CocoaPods Podspec for Static Library

新建 podspec 可以用命令 pod spec create YourLibrary 自动生成 YourLibrary.podspec，然后根据具体项目进行修改。对于 libYourLibrary.a 形式的静态库需要注意的地方:

s.source_files = '*.h'
s.preserve_paths = 'libYourLibrary.a'
s.library = 'YourLibrary'
s.xcconfig = { 'LIBRARY_SEARCH_PATHS' => '$(PODS_ROOT)/YourLibrary' }

preserve_paths 可以用 *.a 模糊匹配或指明静态库名，LIBRARY_SEARCH_PATHS 指定路径。

参考 CocoaPod/Podspec and *.framework