ruby-debug19のインストール

あるRailsプロジェクトでbundle installした際に下記のエラが発生したので、その対応について対策を書いておきます。

```
Installing linecache19 (0.5.12) with native extensions
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

        /home/hirotaka/.rvm/rubies/ruby-1.9.3-head/bin/ruby extconf.rb --with-ruby-include=/home/hirotaka/.rvm/rubies/ruby-1.9.3-head/
checking for vm_core.h... no
/home/hirotaka/.rvm/gems/ruby-1.9.3-head@spree-extension/gems/ruby_core_source-0.1.5/lib/ruby_core_source.rb:39: Use RbConfig instead of obsolete and deprecated Config.
checking for vm_core.h... no
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
        --with-opt-dir
        --with-opt-include
        --without-opt-include=${opt-dir}/include
        --with-opt-lib
        --without-opt-lib=${opt-dir}/lib
        --with-make-prog
        --without-make-prog
        --srcdir=.
        --curdir
        --ruby=/home/hirotaka/.rvm/rubies/ruby-1.9.3-head/bin/ruby
        --with-ruby-dir
        --without-ruby-dir
        --with-ruby-include=${ruby-dir}/include
        --with-ruby-lib
        --without-ruby-lib=${ruby-dir}/lib
/home/hirotaka/.rvm/gems/ruby-1.9.3-head@spree-extension/gems/ruby_core_source-0.1.5/lib/contrib/uri_ext.rb:268:in `block (2 levels) in read': Looking for http://ftp.ruby-lang.org/pub/ruby/1.9/ruby-1.9.3-p173.tar.gz and all I got was a 404! (URI::NotFoundError)
        from /home/hirotaka/.rvm/rubies/ruby-1.9.3-head/lib/ruby/1.9.1/net/http.rb:1322:in `block (2 levels) in transport_request'
        from /home/hirotaka/.rvm/rubies/ruby-1.9.3-head/lib/ruby/1.9.1/net/http.rb:2671:in `reading_body'
        from /home/hirotaka/.rvm/rubies/ruby-1.9.3-head/lib/ruby/1.9.1/net/http.rb:1321:in `block in transport_request'
        from /home/hirotaka/.rvm/rubies/ruby-1.9.3-head/lib/ruby/1.9.1/net/http.rb:1316:in `catch'
        from /home/hirotaka/.rvm/rubies/ruby-1.9.3-head/lib/ruby/1.9.1/net/http.rb:1316:in `transport_request'
        from /home/hirotaka/.rvm/rubies/ruby-1.9.3-head/lib/ruby/1.9.1/net/http.rb:1293:in `request'
        from /home/hirotaka/.rvm/rubies/ruby-1.9.3-head/lib/ruby/1.9.1/net/http.rb:1286:in `block in request'
        from /home/hirotaka/.rvm/rubies/ruby-1.9.3-head/lib/ruby/1.9.1/net/http.rb:745:in `start'
        from /home/hirotaka/.rvm/rubies/ruby-1.9.3-head/lib/ruby/1.9.1/net/http.rb:1284:in `request'
        from /home/hirotaka/.rvm/gems/ruby-1.9.3-head@spree-extension/gems/ruby_core_source-0.1.5/lib/contrib/uri_ext.rb:239:in `block in read'
        from /home/hirotaka/.rvm/gems/ruby-1.9.3-head@spree-extension/gems/ruby_core_source-0.1.5/lib/contrib/uri_ext.rb:286:in `connect'
        from /home/hirotaka/.rvm/gems/ruby-1.9.3-head@spree-extension/gems/ruby_core_source-0.1.5/lib/contrib/uri_ext.rb:234:in `read'
        from /home/hirotaka/.rvm/gems/ruby-1.9.3-head@spree-extension/gems/ruby_core_source-0.1.5/lib/contrib/uri_ext.rb:128:in `download'
        from /home/hirotaka/.rvm/gems/ruby-1.9.3-head@spree-extension/gems/ruby_core_source-0.1.5/lib/ruby_core_source.rb:55:in `block in create_makefile_with_core'
        from /home/hirotaka/.rvm/rubies/ruby-1.9.3-head/lib/ruby/1.9.1/tempfile.rb:320:in `open'
        from /home/hirotaka/.rvm/gems/ruby-1.9.3-head@spree-extension/gems/ruby_core_source-0.1.5/lib/ruby_core_source.rb:51:in `create_makefile_with_core'
        from extconf.rb:19:in `<main>'
Requesting http://ftp.ruby-lang.org/pub/ruby/1.9/ruby-1.9.3-p173.tar.gz


Gem files will remain installed in /home/hirotaka/.rvm/gems/ruby-1.9.3-head@spree-extension/gems/linecache19-0.5.12 for inspection.
Results logged to /home/hirotaka/.rvm/gems/ruby-1.9.3-head@spree-extension/gems/linecache19-0.5.12/ext/trace_nums/gem_make.out

An error occured while installing linecache19 (0.5.12), and Bundler cannot continue.
Make sure that `gem install linecache19 -v '0.5.12'` succeeds before bundling.
```

ruby-debug19をいれようとした際に、vm_core.hが見つからずに発生してしまっているようです。

rubyのソースの場所を指定します。私の場合はrvm経由でいれているので下記の通りになります。

```
$ gem install ruby-debug19 -- --with-ruby-include=\$rvm_path/src/ruby-1.9.3-head/
```