current directory: /home/anatol/sources/vagrant/vendor/bundle/ruby/2.3.0/gems/unf_ext-0.0.7.1/ext/unf_ext
/usr/bin/ruby -r ./siteconf20160108-18494-1wty3fc.rb extconf.rb
checking for main() in -lstdc++... yes
creating Makefile

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

  /home/anatol/sources/vagrant/vendor/bundle/ruby/2.3.0/extensions/x86_64-linux/2.3.0/unf_ext-0.0.7.1/mkmf.log

current directory: /home/anatol/sources/vagrant/vendor/bundle/ruby/2.3.0/gems/unf_ext-0.0.7.1/ext/unf_ext
make "DESTDIR=" clean

current directory: /home/anatol/sources/vagrant/vendor/bundle/ruby/2.3.0/gems/unf_ext-0.0.7.1/ext/unf_ext
make "DESTDIR="
compiling unf.cc
linking shared-object unf_ext.so

current directory: /home/anatol/sources/vagrant/vendor/bundle/ruby/2.3.0/gems/unf_ext-0.0.7.1/ext/unf_ext
make "DESTDIR=" install
/usr/bin/install -c -m 0755 unf_ext.so ./.gem.20160108-18494-lo1790