Giving gem options to bundler install.

As I work more with ArchLinux...  I discovered bundler config options.

For gherkin it seems I need to do this:
gem install gherkin -- --with-cflags="-std=c99"

Yet, in bundler it's not obvious how to pass these along.  You can't do it in the Gemfile -- and you might not want to since another machine could have a different environment.

To pass these flags you create a configuration for the build, which is stored in your machines config only.

From Bundler Gemfile docs:

BUILD OPTIONS

You can use bundle config to give bundler the flags to pass to the gem installer every time bundler tries to install a particular gem.

A very common example, the mysql gem, requires Snow Leopard users to pass configuration flags to gem install to specify where to find themysql_config executable.

gem install mysql -- --with-mysql-config=/usr/local/mysql/bin/mysql_config

Since the specific location of that executable can change from machine to machine, you can specify these flags on a per-machine basis.

bundle config build.mysql --with-mysql-config=/usr/local/mysql/bin/mysql_config

After running this command, every time bundler needs to install themysql gem, it will pass along the flags you specified.

First spotted here:

http://stackoverflow.com/questions/5167829/how-can-i-pass-a-paramater-for-gem-installation-when-i-run-bundle-install