笔记下编译时遇到的问题，以及解决方法(同样是不定时更新)
4月14日
在编译-选项-arch=armv7的时候，提示出现“ -ld: library not found for -lcrt1.3.1.o”，之所以会出现错误，摘取stackOverflow的一段回答
crt1.3.1.ois a library that was included in older iOSes (and thus, their SDKs) but is no longer present in newer SDKs. However, when the project's Deployment Target is set to an older iOS (<6.0, as @Sandy has found), Xcode still tries linking against it.
To keep supporting iOS 5.x in newer Xcodes, one only needs to copycrt1.3.1.ofrom an older Xcode to the appropriate…/usr/lib/dir in the newer Xcode. Xcode will only usecrt1.3.1.oif the Deployment Target is <6.0— for projects with a Deployment Target ≥6.0crt1.3.1.oremains unused and the resulting linked binary is identical to what it was pre-…/usr/lib/crt1.3.1.o-addition
所以iOS环境下在编译ffmpeg的时候，最简单的解决方案是将“-miphoneos-version-min”设置为大于等于6.0
