$ bundle install
Fetching gem metadata from https://rubygems.org/........
Using rake 11.1.2
Using CFPropertyList 2.3.3
Using i18n 0.7.0
Using json 1.8.3
Using minitest 5.8.4
Using thread_safe 0.3.5
Using tzinfo 1.2.2
Using activesupport 4.2.4
Using builder 3.2.2
Using erubis 2.7.0
Using mini_portile2 2.0.0
Fetching nokogiri 1.6.7.2
Installing nokogiri 1.6.7.2 with native extensions
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

current directory:
/media/mcgoy/CD25-ED8E/Upwork/EVSlideShow/Rails/vendor/bundle/ruby/2.1.0/gems/nokogiri-1.6.7.2/ext/nokogiri
/usr/share/rvm/rubies/ruby-2.1.5/bin/ruby -r ./siteconf20190123-15188-1qpzj0b.rb extconf.rb
--use-system-libraries
checking if the C compiler accepts ... *** 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
    --without-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=/usr/share/rvm/rubies/ruby-2.1.5/bin/ruby
    --help
    --clean
/usr/share/rvm/rubies/ruby-2.1.5/lib/ruby/2.1.0/mkmf.rb:456:in `try_do': The compiler failed to
generate an executable file. (RuntimeError)
You have to install development tools first.
    from /usr/share/rvm/rubies/ruby-2.1.5/lib/ruby/2.1.0/mkmf.rb:571:in `block in try_compile'
    from /usr/share/rvm/rubies/ruby-2.1.5/lib/ruby/2.1.0/mkmf.rb:522:in `with_werror'
    from /usr/share/rvm/rubies/ruby-2.1.5/lib/ruby/2.1.0/mkmf.rb:571:in `try_compile'
    from extconf.rb:80:in `nokogiri_try_compile'
    from extconf.rb:87:in `block in add_cflags'
    from /usr/share/rvm/rubies/ruby-2.1.5/lib/ruby/2.1.0/mkmf.rb:621:in `with_cflags'
    from extconf.rb:86:in `add_cflags'
    from extconf.rb:336:in `<main>'

To see why this extension failed to compile, please check the mkmf.log which can be found here:

/media/mcgoy/CD25-ED8E/Upwork/EVSlideShow/Rails/vendor/bundle/ruby/2.1.0/extensions/x86_64-linux/2.1.0/nokogiri-1.6.7.2/mkmf.log

extconf failed, exit code 1

Gem files will remain installed in
/media/mcgoy/CD25-ED8E/Upwork/EVSlideShow/Rails/vendor/bundle/ruby/2.1.0/gems/nokogiri-1.6.7.2
for inspection.
Results logged to
/media/mcgoy/CD25-ED8E/Upwork/EVSlideShow/Rails/vendor/bundle/ruby/2.1.0/extensions/x86_64-linux/2.1.0/nokogiri-1.6.7.2/gem_make.out

An error occurred while installing nokogiri (1.6.7.2), and Bundler cannot continue.
Make sure that `gem install nokogiri -v '1.6.7.2' --source 'https://rubygems.org/'` succeeds
before bundling.

In Gemfile:
  rails was resolved to 4.2.4, which depends on
    actionmailer was resolved to 4.2.4, which depends on
      actionpack was resolved to 4.2.4, which depends on
        actionview was resolved to 4.2.4, which depends on
          rails-dom-testing was resolved to 1.0.7, which depends on
            nokogiri

$ gem install nokogiri -v 1.6.7.2
Building native extensions. This could take a while...
Successfully installed nokogiri-1.6.7.2
Parsing documentation for nokogiri-1.6.7.2
Done installing documentation for nokogiri after 2 seconds
1 gem installed