Support for the patch that gets MRI 1.8.7 to build on Fedora 16+.

[pwnall]

I couldn't use ruby-build to get MRI 1.8.7 on my Fedora system, and I wanted it so I could test my gems on 1.8.7, so I read up on it and made it work.

I tried to keep the bash clean and simple, but I'm open to any feedback on making the diff better. I hope you'll consider merging this, so rbenv install 1.8.7 "just works" for Fedora users too.

Bug question on StackOverflow: http://stackoverflow.com/questions/6134456/error-while-installing-ruby-1-8-7-on-fedora-15/6321482#6321482
Bug with patch on the MRI bug tracker: http://bugs.ruby-lang.org/issues/5108

[sstephenson]

Thanks for the pull request.

As a rule we don't do any source code patching in our bundled definitions. The goal is for ruby-build's installation to be just what you'd get if you downloaded the source yourself and ran ./configure && make install. Applying patches like these would be akin to taking responsibility for maintenance of the 1.8 tree, and that's not what we plan to do.

The Ruby core team suggests compiling with --without-dl in this ticket: http://bugs.ruby-lang.org/issues/5108 You can do that with ruby-build by setting the CONFIGURE_OPTS environment variable:

$ CONFIGURE_OPTS="--without-dl" rbenv install 1.8.7-p370

[sstephenson]

Also note that you're free to maintain your own set of definitions that include this patch. Both the ruby-build and rbenv install commands accept a path to a custom definition file in place of a built-in definition name.

[pwnall]

@sstephenson Thank you very much for taking the time to write a thorough explanation!

Is there any chance you would consider pulling in the patch functionality, so I can easily write definitions that apply patches? If so, I can turn that into a separate commit.

Thanks for rbenv!