title: CocoaPods installation failed "Failed to build gem native extension"
body: <p>I cannot install the cocoapods to my Mac Catalina by the following command:</p>
  <pre><code>sudo gem install cocoapods
  </code></pre>
  <p>Here is the error message from the terminal:</p>
  <pre><code>
  Building native extensions. This could take a while...
  ERROR:  Error installing cocoapods:
      ERROR: Failed to build gem native extension.
  
      current directory: /Library/Ruby/Gems/2.6.0/gems/ffi-1.13.1/ext/ffi_c
  /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/ruby -I /Library/Ruby/Site/2.6.0 -r ./siteconf20201117-5613-1jjoznr.rb extconf.rb
  *** 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/$(RUBY_BASE_NAME)
      --with-ffi_c-dir
      --without-ffi_c-dir
      --with-ffi_c-include
      --without-ffi_c-include=${ffi_c-dir}/include
      --with-ffi_c-lib
      --without-ffi_c-lib=${ffi_c-dir}/lib
      --enable-system-libffi
      --disable-system-libffi
      --with-libffi-config
      --without-libffi-config
      --with-pkg-config
      --without-pkg-config
  /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:672:in `try_ldflags'
      from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:1832:in `pkg_config'
      from extconf.rb:9:in `system_libffi_usable?'
      from extconf.rb:42:in `&lt;main&gt;'
  
  To see why this extension failed to compile, please check the mkmf.log which can be found here:
  
    /Library/Ruby/Gems/2.6.0/extensions/universal-darwin-19/2.6.0/ffi-1.13.1/mkmf.log
  
  extconf failed, exit code 1
  </code></pre>
  <p>Here is the error shown at the <code> /Library/Ruby/Gems/2.6.0/extensions/universal-darwin-19/2.6.0/ffi-1.13.1/mkmf.log</code>:</p>
  <pre><code>| pkg-config --libs libffi
  =&gt; &quot;-lffi\n&quot;
  &quot;xcrun clang -o conftest -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/include/ruby-2.6.0/universal-darwin19 -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/include/ruby-2.6.0/ruby/backward -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/include/ruby-2.6.0 -I. -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -D_DARWIN_UNLIMITED_SELECT -D_REENTRANT    -g -Os -pipe -DHAVE_GCC_ATOMIC_BUILTINS conftest.c  -L. -L/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib -L. -L/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.Internal.sdk/usr/local/lib   -arch x86_64   -lruby.2.6   &quot;
  In file included from conftest.c:1:
  In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/include/ruby-2.6.0/ruby.h:33:
  /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/include/ruby-2.6.0/ruby/ruby.h:24:10: fatal error: 'ruby/config.h' file not found
  #include &quot;ruby/config.h&quot;
           ^~~~~~~~~~~~~~~
  /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/include/ruby-2.6.0/ruby/ruby.h:24:10: note: did not find header 'config.h' in framework 'ruby' (loaded from '/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/System/Library/Frameworks')
  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>I have installed the Xcode 12.2(12B45b) to Mac and selected it as the Command Line Tools.
  I am very confused with these messages. Thank you very much !!!</p>