我已经安装了 pophealth 的所有依赖项：
“ https://github.com/pophealth/popHealth/wiki/Installation ”
但是当我运行时，Bundle Install我收到以下错误：
Gem:Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
/usr/bin/ruby1.8 extconf.rb
extconf.rb:1:in 'require': no such file to load -- mkmf (LoadError)
from extconf.rb:1
Gem Files will remain installed in /home/pophealth/.bundler/tmp/3335/gems/bson_ext-1.5.1 for inspection
results logged to /home/pophealth/.bundler/tmp/3335/gems/bson_ext-1.5.1/ext/cbson/gem_make.out
An error occurred while installing bson_ext (1.5.1), and bundler cannot continue.
Make sure that 'gem install bson_ext -v '1.5.1'' succeeds before bundling.
当我运行时，gem install bson_ext -v '1.5.1'我收到以下错误
