current directory: /usr/local/rvm/gems/ruby-3.0.2/gems/mysql2-0.5.3/ext/mysql2
/usr/local/rvm/rubies/ruby-3.0.2/bin/ruby -I /usr/local/rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0 -r ./siteconf20211109-155843-qq98gx.rb extconf.rb
checking for rb_absint_size()... yes
checking for rb_absint_singlebit_p()... yes
checking for rb_wait_for_single_fd()... yes
*** 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/local/rvm/rubies/ruby-3.0.2/bin/$(RUBY_BASE_NAME)
	--with-mysql-dir
	--without-mysql-dir
	--with-mysql-include
	--without-mysql-include=${mysql-dir}/include
	--with-mysql-lib
	--without-mysql-lib=${mysql-dir}/lib
	--with-mysql-config
	--without-mysql-config
	--with-mysqlclient-dir
	--without-mysqlclient-dir
	--with-mysqlclient-include
	--without-mysqlclient-include=${mysqlclient-dir}/include
	--with-mysqlclient-lib
	--without-mysqlclient-lib=${mysqlclient-dir}/lib
	--with-mysqlclientlib
	--without-mysqlclientlib
/usr/local/rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0/mkmf.rb:1050:in `block in find_library': undefined method `split' for nil:NilClass (NoMethodError)
	from /usr/local/rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0/mkmf.rb:1050:in `collect'
	from /usr/local/rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0/mkmf.rb:1050:in `find_library'
	from extconf.rb:87:in `<main>'

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

  /usr/local/rvm/gems/ruby-3.0.2/extensions/x86_64-linux/3.0.0/mysql2-0.5.3/mkmf.log

extconf failed, exit code 1