bundle install時にMySQLのエラーが発生

# bundle install時にMySQLのエラーが発生

RUNTEQのRuby on Railsの技術試験を受験し、環境構築をしていた際に以下のエラーが発生しました。

## 入力したコマンド

```:ターミナル
bundle install --path=vendor/bundle
```


## 発生したエラー

```:ターミナル
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    current directory: /Users/atsukikomuro/projects/133_atsuki1224_runteq_selection_rails_basic/vendor/bundle/ruby/2.6.0/gems/mysql2-0.5.2/ext/mysql2
/Users/atsukikomuro/.rbenv/versions/2.6.4/bin/ruby -I /Users/atsukikomuro/.rbenv/versions/2.6.4/lib/ruby/2.6.0 -r ./siteconf20200226-71382-91nqge.rb extconf.rb
checking for rb_absint_size()... yes
checking for rb_absint_singlebit_p()... yes
checking for rb_wait_for_single_fd()... yes
-----
Using mysql_config at /usr/local/opt/mysql@5.6/bin/mysql_config
-----
checking for mysql.h... yes
checking for errmsg.h... yes
checking for SSL_MODE_DISABLED in mysql.h... no
checking for MYSQL_OPT_SSL_ENFORCE in mysql.h... no
checking for MYSQL.net.vio in mysql.h... yes
checking for MYSQL.net.pvio in mysql.h... no
checking for MYSQL_ENABLE_CLEARTEXT_PLUGIN in mysql.h... yes
checking for SERVER_QUERY_NO_GOOD_INDEX_USED in mysql.h... yes
checking for SERVER_QUERY_NO_INDEX_USED in mysql.h... yes
checking for SERVER_QUERY_WAS_SLOW in mysql.h... yes
checking for MYSQL_OPTION_MULTI_STATEMENTS_ON in mysql.h... yes
checking for MYSQL_OPTION_MULTI_STATEMENTS_OFF in mysql.h... yes
checking for my_bool in mysql.h... yes
-----
Don't know how to set rpath on your system, if MySQL libraries are not in path mysql2 may not load
-----
-----
Setting libpath to /usr/local/opt/mysql@5.6/lib
-----
creating Makefile

current directory: /Users/atsukikomuro/projects/133_atsuki1224_runteq_selection_rails_basic/vendor/bundle/ruby/2.6.0/gems/mysql2-0.5.2/ext/mysql2
make "DESTDIR=" clean

current directory: /Users/atsukikomuro/projects/133_atsuki1224_runteq_selection_rails_basic/vendor/bundle/ruby/2.6.0/gems/mysql2-0.5.2/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/atsukikomuro/projects/133_atsuki1224_runteq_selection_rails_basic/vendor/bundle/ruby/2.6.0/gems/mysql2-0.5.2 for inspection.
Results logged to /Users/atsukikomuro/projects/133_atsuki1224_runteq_selection_rails_basic/vendor/bundle/ruby/2.6.0/extensions/x86_64-darwin-18/2.6.0/mysql2-0.5.2/gem_make.out

An error occurred while installing mysql2 (0.5.2), and Bundler cannot continue.
Make sure that `gem install mysql2 -v '0.5.2' --source 'https://rubygems.org/'` succeeds before bundling.

In Gemfile:
  mysql2
```

## 解決策
以下のコマンドを入力後にbundle installを行うことで正常に終了しました。

```:ターミナル
bundle config --local build.mysql2 "--with-ldflags=-L/usr/local/opt/openssl/lib --with-cppflags=-I/usr/local/opt/openssl/include"
```

## 原因
後日記入します。

## 参考文献
[RailsプロジェクトでMySQLがbundle installできなかった](https://qiita.com/akito19/items/e1dc54f907987e688cc0)
[bundle installでmysql2がエラーになる件](https://qiita.com/SAYJOY/items/dd7c8fc7a3647e7ff969)