title: Error installing rails: 'ruby/config.h' file not found (Catalina 10.15.7)
body: <p>Hey there I have tried all kinds of work arounds for similar issues that i've seen on stack overflow but can't get anything to work when trying to install rails.</p>
  <p>This is the fatal error I get. I have macOS Catalina version 10.15.7</p>
  <pre><code>1 error generated.
  checked program was:
  /* begin */
  1: #include &quot;ruby.h&quot;
  2: 
  3: int main(int argc, char **argv)
  4: {
  5:   return 0;
  6: }
  /* end */
  </code></pre>
  <p>Here is a little more detail from my terminal</p>
  <pre><code>You have to install development tools first.
      from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:585:in `block in try_compile'
      from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:534:in `with_werror'
      from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:585:in `try_compile'
      from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:1109:in `block in have_header'
      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:1108:in `have_header'
      from extconf.rb:15:in `&lt;main&gt;'
  </code></pre>
  <p>Thank you and I appreciate any help.</p>