【AmazonLinux2】MySQL2のGemをインストールする際にエラー

##MySQLの調子が悪かったのでアンインストールして再インストール
```
gem uninstall mysql2
gem install mysql2
```
- エラーが発生

```
Fetching mysql2 0.5.3
Installing mysql2 0.5.3 with native extensions
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    current directory: /home/takumi/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/mysql2-0.5.3/ext/mysql2
/home/takumi/.rbenv/versions/2.5.1/bin/ruby -r ./siteconf20200619-26162-iq2nwv.rb extconf.rb --with-ldflags=-L/usr/local/opt/openssl/lib
checking for rb_absint_size()... yes
checking for rb_absint_singlebit_p()... yes
checking for rb_wait_for_single_fd()... yes
checking for -lmysqlclient... no
-----
mysql client 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.

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=/home/takumi/.rbenv/versions/2.5.1/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=${mysql-dir}/lib
	--with-mysql-config
	--without-mysql-config
	--with-mysql-dir
	--without-mysql-dir
	--with-mysql-include
	--without-mysql-include=${mysql-dir}/include
	--with-mysql-lib
	--without-mysql-lib=${mysql-dir}/lib
	--with-mysqlclientlib
	--without-mysqlclientlib

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

  /home/takumi/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/extensions/x86_64-linux/2.5.0/mysql2-0.5.3/mkmf.log

extconf failed, exit code 1

Gem files will remain installed in /home/takumi/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/mysql2-0.5.3 for inspection.
Results logged to /home/takumi/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/extensions/x86_64-linux/2.5.0/mysql2-0.5.3/gem_make.out

An error occurred while installing mysql2 (0.5.3), and Bundler cannot continue.
Make sure that `gem install mysql2 -v '0.5.3' --source 'https://rubygems.org/'` succeeds before bundling.

In Gemfile:
  mysql2

```
言われた通り下記のコマンドを実行してもエラーが発生した。

```
gem install mysql2 -v '0.5.3' --source 'https://rubygems.org/'
```

##解決策
```
mysql client 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.
```
エラー文にある、この中の'sudo yum install mysql-devel'を実行した。

```
$ sudo yum install mysql-devel
読み込んだプラグイン:extras_suggestions, langpacks, priorities, update-motd
amzn2-core                                                                                                                                                                         | 3.7 kB  00:00:00     
amzn2extra-docker                                                                                                                                                                  | 3.0 kB  00:00:00     
amzn2extra-nginx1                                                                                                                                                                  | 1.8 kB  00:00:00     
mysql-connectors-community                                                                                                                                                         | 2.5 kB  00:00:00     
mysql-tools-community                                                                                                                                                              | 2.5 kB  00:00:00     
mysql57-community                                                                                                                                                                  | 2.5 kB  00:00:00     
nodesource                                                                                                                                                                         | 2.5 kB  00:00:00     
33 packages excluded due to repository priority protections
依存性の解決をしています
--> トランザクションの確認を実行しています。
---> パッケージ mysql-community-devel.x86_64 0:5.7.30-1.el7 を インストール
--> 依存性解決を終了しました。

依存性を解決しました

==========================================================================================================================================================================================================
 Package                                                アーキテクチャー                        バージョン                                       リポジトリー                                        容量
==========================================================================================================================================================================================================
インストール中:
 mysql-community-devel                                  x86_64                                  5.7.30-1.el7                                     mysql57-community                                  3.7 M

トランザクションの要約
==========================================================================================================================================================================================================
インストール  1 パッケージ

総ダウンロード容量: 3.7 M
インストール容量: 20 M
Is this ok [y/d/N]: y
Downloading packages:
mysql-community-devel-5.7.30-1.el7.x86_64.rpm                                                                                                                                      | 3.7 MB  00:00:00     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  インストール中          : mysql-community-devel-5.7.30-1.el7.x86_64                                                                                                                                 1/1 
  検証中                  : mysql-community-devel-5.7.30-1.el7.x86_64                                                                                                                                 1/1 

インストール:
  mysql-community-devel.x86_64 0:5.7.30-1.el7                                                                                                                                                             

完了しました!

```

bundle installを実行。無事通りました！

```
$ bundle install
~~
Bundle complete! 37 Gemfile dependencies, 136 gems now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.
```