Redmine

I want to install redmine, refer to:http://www.redmine.org/projects/redmine/wiki/RedmineInstall and I go to step4.,and execute "bundle install --without development test",got an error, then execute "sudo gem install json -v '1.8.1'" ,got another error. and I stuck here ,I don't know how to fix this two error. This is my command & output below:

yayaigo-2:redmine yayaigo$ bundle install --without development test
Fetching gem metadata from https://rubygems.org/.........
Fetching additional metadata from https://rubygems.org/..
Resolving dependencies...
Using rake 10.1.1
Using i18n 0.6.9
Using multi_json 1.9.2
Using activesupport 3.2.17
Using builder 3.0.0
Using activemodel 3.2.17
Using erubis 2.7.0
Using journey 1.0.4
Using rack 1.4.5
Using rack-cache 1.2
Using rack-test 0.6.2
Using hike 1.2.3
Using tilt 1.4.1
Using sprockets 2.2.2
Using actionpack 3.2.17
Using mime-types 1.25.1
Using polyglot 0.3.4
Using treetop 1.4.15
Using mail 2.5.4
Using actionmailer 3.2.17
Using arel 3.0.3
Using tzinfo 0.3.39
Using activerecord 3.2.17
Using activeresource 3.2.17
Using awesome_nested_set 2.1.6
Using bundler 1.6.2
Using coderay 1.1.0
Using rack-ssl 1.3.4

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

/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb 
creating Makefile

make "DESTDIR=" clean

make "DESTDIR="
compiling generator.c
linking shared-object json/ext/generator.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: *** [generator.bundle] Error 1

make failed, exit code 2

Gem files will remain installed in /var/folders/vc/skvcsqcn33s4snfd9jj5xwfc0000gn/T/bundler20140419-48941-iht3ml/json-1.8.1/gems/json-1.8.1 for inspection.
Results logged to /var/folders/vc/skvcsqcn33s4snfd9jj5xwfc0000gn/T/bundler20140419-48941-iht3ml/json-1.8.1/extensions/universal-darwin-13/2.0.0/json-1.8.1/gem_make.out
An error occurred while installing json (1.8.1), and Bundler cannot continue.
Make sure that `gem install json -v '1.8.1'` succeeds before bundling.
yayaigo-2:redmine yayaigo$ gem install json -v '1.8.1'
ERROR: While executing gem ... (Errno::EACCES)
Permission denied - /Library/Ruby/Gems/2.0.0/gems/json-1.8.1/.gitignore
yayaigo-2:redmine yayaigo$ sudo gem install json -v '1.8.1'**
Building native extensions. This could take a while...
ERROR: Error installing json:
ERROR: Failed to build gem native extension.

/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb
creating Makefile

make "DESTDIR=" clean

make "DESTDIR="
compiling generator.c
linking shared-object json/ext/generator.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: *** [generator.bundle] Error 1

make failed, exit code 2

Gem files will remain installed in /Library/Ruby/Gems/2.0.0/gems/json-1.8.1 for inspection.
Results logged to /Library/Ruby/Gems/2.0.0/extensions/universal-darwin-13/2.0.0/json-1.8.1/gem_make.out

Any know how to fix that? Thanks. Regards.