gem install mysql2
Building native extensions.  This could take a while...
ERROR:  Error installing mysql2:
    ERROR: Failed to build gem native extension.

    /Users/frank/.rbenv/versions/2.2.4/bin/ruby -r ./siteconf20161017-40878-1pj8mbn.rb extconf.rb
checking for ruby/thread.h... yes
checking for rb_thread_call_without_gvl() in ruby/thread.h... yes
checking for rb_thread_blocking_region()... no
checking for rb_wait_for_single_fd()... yes
checking for rb_hash_dup()... yes
checking for rb_intern3()... yes
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Using mysql_config at /usr/local/bin/mysql_config
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checking for mysql.h... yes
checking for errmsg.h... yes
checking for mysqld_error.h... yes
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Don't know how to set rpath on your system, if MySQL libraries are not in path mysql2 may not load
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Setting libpath to /usr/local/Cellar/mariadb/10.1.18/lib
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creating Makefile

make "DESTDIR=" clean

make "DESTDIR="
compiling client.c
compiling infile.c
compiling mysql2_ext.c
compiling result.c
compiling statement.c
linking shared-object mysql2/mysql2.bundle
ld: library not found for -lssl
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [mysql2.bundle] Error 1

make failed, exit code 2

Gem files will remain installed in /Users/frank/.rbenv/versions/2.2.4/lib/ruby/gems/2.2.0/gems/mysql2-0.4.4 for inspection.
Results logged to /Users/frank/.rbenv/versions/2.2.4/lib/ruby/gems/2.2.0/extensions/x86_64-darwin-16/2.2.0-static/mysql2-0.4.4/gem_make.out