环境
mac系统版本：macOS Mojave10.14.6
ruby:ruby 2.3.7p456 (2018-03-28 revision 63024)
cocoapods: 1.5.0
issue
拿到一个新项目(cocoapods 1.9.0)，使用sudo gem install cocoapods更新仓库！报错如下：
Building native extensions. This could take a while...
ERROR: Error installing cocoapods:
ERROR: Failed to build gem native extension.
current directory: /Library/Ruby/Gems/2.3.0/gems/ffi-1.12.2/ext/ffi_c
/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/bin/ruby -r ./siteconf20200309-13044-14m1r7i.rb extconf.rb
mkmf.rb can't find header files for ruby at /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/include/ruby.h
extconf failed, exit code 1
Gem files will remain installed in /Library/Ruby/Gems/2.3.0/gems/ffi-1.12.2 for inspection.
Results logged to /Library/Ruby/Gems/2.3.0/extensions/universal-darwin-18/2.3.0/ffi-1.12.2/gem_make.out
尝试了gem update --system、xcode-select --install、sudo apt-get install ruby-dev等方法未解决该问题！
解决方法
open /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg
Done installing documentation for ffi,
ethon, typhoeus, netrc, cocoapods-core, claide,
cocoapods-deintegrate, cocoapods-downloader,
cocoapods-plugins, cocoapods-search,
cocoapods-stats, cocoapods-trunk, cocoapods-try,
molinillo, atomos, CFPropertyList, colored2,
nanaimo, xcodeproj, escape, fourflusher, gh_inspector,
ruby-macho, cocoapods after 50 seconds
24 gems installed
