Clang build error when trying to install Jekyll

Question

I am trying to install Jekyll using the instruction on this page (https://help.github.com/articles/using-jekyll-with-pages). However, at the second step, bundle install, the following is output

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb 
checking for main() in -lc... yes
creating Makefile

make "DESTDIR=" clean

make "DESTDIR="
compiling redcloth_attributes.c
compiling redcloth_inline.c
compiling redcloth_scan.c
linking shared-object redcloth_scan.bundle
clang: error: unknown argument: '-multiply_definedsuppress' [-Wunused-command-line-argument-hard-error-in-future]
clang: note: this will be a hard error (cannot be downgraded to a warning) in the future
make: *** [redcloth_scan.bundle] Error 1

make failed, exit code 2

Gem files will remain installed in /var/folders/39/fxww36m16ddggmf4plpl3mv40000gn/T/bundler20140403-1735-6tlte3/RedCloth-4.2.9/gems/RedCloth-4.2.9 for inspection.
Results logged to /var/folders/39/fxww36m16ddggmf4plpl3mv40000gn/T/bundler20140403-1735-6tlte3/RedCloth-4.2.9/extensions/universal-darwin-13/2.0.0/RedCloth-4.2.9/gem_make.out
An error occurred while installing RedCloth (4.2.9), and Bundler cannot continue.
Make sure that `gem install RedCloth -v '4.2.9'` succeeds before bundling.

clang --version outputs

Apple LLVM version 5.1 (clang-503.0.38) (based on LLVM 3.4svn)
Target: x86_64-apple-darwin13.1.0
Thread model: posix

on my machine, and Ruby is version 2.0.0p247.

I've seen a number of other people's questions about this, but none of them have the same issue, nor do the solutions suggested to them seem particularly relevant, apart from the idea of somehow getting bundler to use GCC instead of Clang, which I don't know how to accomplish. One idea I have is to get Clang to treat this as a warning instead of an error, as the message implies is possible in this version, but I don't know how I would do that either, especially in the context of a terminal command like bundle install. How can I fix this?

Answer 1

I used ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future bundle install to treat the error as a warning.

Answer 2

sudo ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future gem install jekyll