fix doc in Makefile
fix doc in Makefile

CJstar/facebook-clang-plugins,caijinyan/facebook-clang-plugins,caijinyan/facebook-clang-plugins,wangwei1237/facebook-clang-plugins,caijinyan/facebook-clang-plugins,wangwei1237/facebook-clang-plugins,caijinyan/facebook-clang-plugins,raphaelamorim/facebook-clang-plugins,raphaelamorim/facebook-clang-plugins,raphaelamorim/facebook-clang-plugins,raphaelamorim/facebook-clang-plugins,wangwei1237/facebook-clang-plugins,CJstar/facebook-clang-plugins,CJstar/facebook-clang-plugins,CJstar/facebook-clang-plugins,wangwei1237/facebook-clang-plugins