bundle installの失敗

前提・実現したいこと

railsでのbundle installをしたいです。

ここに質問の内容を詳しく書いてください。
railsでアプリを作りたいのですが、bundle installをするとたくさんのエラーが発生します。
Qiitaなどで解決方法を探したのですが、どうも解決することが出来ませんでした。
読みづらいですが、助けていただいたら幸いです。
よろしくお願いいたします。

発生している問題・エラーメッセージ

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

該当のソースコード

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

current directory: /Users/rt/Desktop/coffeeApp/vendor/bundle/ruby/2.6.0/gems/racc-1.5.2/ext/racc/cparse

/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/ruby -I /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0 -r
./siteconf20210106-54173-1miyqpa.rb extconf.rb
checking for rb_ary_subseq()... *** 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=/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/$(RUBY_BASE_NAME)
/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:467:in try_do': The compiler failed to generate an executable file. (RuntimeError) You have to install development tools first. from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:546:in block in try_link0'
from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/tmpdir.rb:93:in mktmpdir' from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:543:in try_link0'
from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:570:in try_link' from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:782:in try_func'
from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:1069:in block in have_func' from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:959:in block in checking_for'
from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:361:in block (2 levels) in postpone' from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:331:in open'
from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:361:in block in postpone' from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:331:in open'
from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:357:in postpone' from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:958:in checking_for'
from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:1068:in have_func' from extconf.rb:6:in <main>'

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

/Users/rt/Desktop/coffeeApp/vendor/bundle/ruby/2.6.0/extensions/universal-darwin-19/2.6.0/racc-1.5.2/mkmf.log

extconf failed, exit code 1

試したこと

https://qiita.com/Ushinji/items/dc79f12f03fabdb7a7a6

この記事を頼りに
export LIBRARY_PATH=$LIBRARY_PATH:/usr/local/opt/openssl/lib/
を実行してもエラー文が消えませんでした。

補足情報（FW/ツールのバージョンなど）

ruby 2.6.3p62 (2019-04-16 revision 67580) [universal.x86_64-darwin19]

railsのバージョンを確認しても、
Could not find gem 'rails (~> 6.0.3, >= 6.0.3.2)' in any of the gem sources listed in your Gemfile.
とエラー文が出るが、bundle installが失敗してしまいます。