Can't install mysql2 gem on macOS Sierra
<p>I'm setting up my development environment in the new <strong>macOS Sierra</strong> .</p>

<p>First of all, I installed <strong>Rbenv</strong>, <strong>Ruby (2.3.1)</strong>, <strong>Homebrew</strong> and so the latest version of <strong>MySQL (5.7.15)</strong>.</p>

<pre><code>$ brew install mysql
$ mysql.server start
</code></pre>

<p>Ok, MySQL was initialized. Time to install the <strong>mysql2</strong> gem...</p>

<pre><code>$ gem install mysql2 -- --with-mysql-config=/usr/local/Cellar/mysql/5.7.15/bin/mysql_config
</code></pre>

<p>But it didn't work.  </p>

<hr>

<pre><code>Building native extensions with: '--with-mysql-config=/usr/local/Cellar/mysql/5.7.15/bin/mysql_config'
This could take a while...
ERROR:  Error installing mysql2:
    ERROR: Failed to build gem native extension.

    current directory: /Users/macuser/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/mysql2-0.4.4/ext/mysql2
/Users/macuser/.rbenv/versions/2.3.1/bin/ruby -r ./siteconf20160921-16853-x1boio.rb extconf.rb --with-mysql-config=/usr/local/Cellar/mysql/5.7.15/bin/mysql_config
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
-----
Using mysql_config at /usr/local/Cellar/mysql/5.7.15/bin/mysql_config
-----
checking for mysql.h... yes
checking for errmsg.h... yes
checking for mysqld_error.h... yes
-----
Dont know how to set rpath on your system, if MySQL libraries are not in path mysql2 may not load
-----
-----
Setting libpath to /usr/local/Cellar/mysql/5.7.15/lib
-----
creating Makefile

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

  /Users/macuser/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/extensions/x86_64-darwin-16/2.3.0-static/mysql2-0.4.4/mkmf.log

current directory: /Users/macuser/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/mysql2-0.4.4/ext/mysql2
make "DESTDIR=" clean

current directory: /Users/macuser/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/mysql2-0.4.4/ext/mysql2
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/macuser/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/mysql2-0.4.4 for inspection.
Results logged to /Users/macuser/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/extensions/x86_64-darwin-16/2.3.0-static/mysql2-0.4.4/gem_make.out
</code></pre>