/opt/jruby-9.1.8.0/bin/gem install pg

Building native extensions. This could take a while...
ERROR: Error installing pg:
ERROR: Failed to build gem native extension.

current directory: /opt/jruby-9.1.8.0/lib/ruby/gems/shared/gems/pg-0.20.0/ext

/opt/jruby-9.1.8.0/bin/jruby -r ./siteconf20170509-12119-12tafom.rb extconf.rb
checking for pg_config... yes
Using config values from /usr/bin/pg_config
RuntimeError: The compiler failed to generate an executable file.
You have to install development tools first.

 try_do at /opt/jruby-9.1.8.0/lib/ruby/stdlib/mkmf.rb:456

try_link0 at /opt/jruby-9.1.8.0/lib/ruby/stdlib/mkmf.rb:541
try_link at /opt/jruby-9.1.8.0/lib/ruby/stdlib/mkmf.rb:556

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=/opt/jruby-9.1.8.0/bin/jruby
--with-pg
--without-pg
--enable-windows-cross
--disable-windows-cross
--with-pg-config
--without-pg-config
--with-pg_config
--without-pg_config
--with-pg-dir
--without-pg-dir
--with-pg-include
--without-pg-include=${pg-dir}/include
--with-pg-lib
--without-pg-lib=${pg-dir}/lib

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

/opt/jruby-9.1.8.0/lib/ruby/gems/shared/extensions/universal-java-1.8/2.3.0/pg-0.20.0/mkmf.log

extconf failed, exit code 1

Gem files will remain installed in /opt/jruby-9.1.8.0/lib/ruby/gems/shared/gems/pg-0.20.0 for inspection.
Results logged to /opt/jruby-9.1.8.0/lib/ruby/gems/shared/extensions/universal-java-1.8/2.3.0/pg-0.20.0/gem_make.out