I tried to build redmine51 in a Poudriere where I have MariaDB 10.11 set as mysql variant.  Redmine depends on databases/rubygem-mysql2 and it failed to build with the following error:

ERROR:  Error installing mysql2-0.5.6.gem:
	ERROR: Failed to build gem native extension.

    current directory: /wrkdirs/usr/ports/databases/rubygem-mysql2/work/stage/usr/local/lib/ruby/gems/3.2/gems/mysql2-0.5.6/ext/mysql2
/usr/local/bin/ruby32 extconf.rb
checking for rb_absint_size()... yes
checking for rb_absint_singlebit_p()... yes
checking for rb_gc_mark_movable()... yes
checking for rb_wait_for_single_fd()... yes
checking for rb_enc_interned_str() in ruby.h... yes
-----
Using mysql_config at /usr/local/bin/mysql_config
-----
checking for mysql.h... no
checking for mysql/mysql.h... no
-----
mysql.h is missing. You may need to 'sudo apt-get install libmariadb-dev', 'sudo apt-get install libmysqlclient-dev' or 'sudo yum install mysql-devel', and try again.
-----
*** 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.


I don't know why it cannot find mysql.h. MariaDB client is installed as dependency. Earlier in the build log:

===>   rubygem-mysql2-0.5.6 depends on shared library: libmariadb.so.3 - not found
===>   Installing existing package /packages/All/mariadb1011-client-10.11.7.pkg
..
..
[pkg.example.com] Extracting mariadb1011-client-10.11.7: .......... done