title: Unable to install cocoa pods
body: <p>I want to install cocoapods on MacOS to run the pod command. But on doing</p>
  <pre><code>sudo gem install cocoa-pods
  </code></pre>
  <p>I get the following:</p>
  <pre><code>Building native extensions. This could take a while...
  ERROR:  Error installing cocoapods:
      ERROR: Failed to build gem native extension.
  
      current directory: /usr/local/lib/ruby/gems/2.7.0/gems/ffi-1.13.1/ext/ffi_c
  /usr/local/opt/ruby/bin/ruby -I /usr/local/Cellar/ruby/2.7.1_2/lib/ruby/2.7.0 -r ./siteconf20200702-22528-1o4wbn0.rb extconf.rb
  checking for ffi.h... *** 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
      --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=/usr/local/Cellar/ruby/2.7.1_2/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=${ffi_c-dir}/lib
      --enable-system-libffi
      --disable-system-libffi
      --with-libffi-config
      --without-libffi-config
      --with-pkg-config
      --without-pkg-config
      --with-ffi-dir
      --without-ffi-dir
      --with-ffi-include
      --without-ffi-include=${ffi-dir}/include
      --with-ffi-lib
      --without-ffi-lib=${ffi-dir}/lib
  /usr/local/Cellar/ruby/2.7.1_2/lib/ruby/2.7.0/mkmf.rb:471:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
  You have to install development tools first.
      from /usr/local/Cellar/ruby/2.7.1_2/lib/ruby/2.7.0/mkmf.rb:613:in `try_cpp'
      from /usr/local/Cellar/ruby/2.7.1_2/lib/ruby/2.7.0/mkmf.rb:1124:in `block in have_header'
      from /usr/local/Cellar/ruby/2.7.1_2/lib/ruby/2.7.0/mkmf.rb:971:in `block in checking_for'
      from /usr/local/Cellar/ruby/2.7.1_2/lib/ruby/2.7.0/mkmf.rb:361:in `block (2 levels) in postpone'
      from /usr/local/Cellar/ruby/2.7.1_2/lib/ruby/2.7.0/mkmf.rb:331:in `open'
      from /usr/local/Cellar/ruby/2.7.1_2/lib/ruby/2.7.0/mkmf.rb:361:in `block in postpone'
      from /usr/local/Cellar/ruby/2.7.1_2/lib/ruby/2.7.0/mkmf.rb:331:in `open'
      from /usr/local/Cellar/ruby/2.7.1_2/lib/ruby/2.7.0/mkmf.rb:357:in `postpone'
      from /usr/local/Cellar/ruby/2.7.1_2/lib/ruby/2.7.0/mkmf.rb:970:in `checking_for'
      from /usr/local/Cellar/ruby/2.7.1_2/lib/ruby/2.7.0/mkmf.rb:1123:in `have_header'
      from extconf.rb:10: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:
  
    /usr/local/lib/ruby/gems/2.7.0/extensions/x86_64-darwin-19/2.7.0/ffi-1.13.1/mkmf.log
  
  extconf failed, exit code 1
  
  Gem files will remain installed in /usr/local/lib/ruby/gems/2.7.0/gems/ffi-1.13.1 for inspection.
  Results logged to /usr/local/lib/ruby/gems/2.7.0/extensions/x86_64-darwin-19/2.7.0/ffi-1.13.1/gem_make.out
  
  </code></pre>
  <p>The mkmf.log file is:</p>
  <pre><code>package configuration for libffi is not found
  &quot;clang -o conftest -I/usr/local/Cellar/ruby/2.7.1_2/include/ruby-2.7.0/x86_64-darwin19 -I/usr/local/Cellar/ruby/2.7.1_2/include/ruby-2.7.0/ruby/backward -I/usr/local/Cellar/ruby/2.7.1_2/include/ruby-2.7.0 -I.  -I/usr/local/opt/libyaml/include -I/usr/local/opt/openssl@1.1/include -I/usr/local/opt/readline/include -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -D_DARWIN_UNLIMITED_SELECT -D_REENTRANT   -O3 -ggdb3 -Wall -Wextra -Wdeprecated-declarations -Wdivision-by-zero -Wimplicit-function-declaration -Wimplicit-int -Wpointer-arith -Wshorten-64-to-32 -Wwrite-strings -Wmissing-noreturn -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wunused-variable -Wextra-tokens  -fno-common -pipe conftest.c  -L. -L/usr/local/Cellar/ruby/2.7.1_2/lib -L/usr/local/opt/libyaml/lib -L/usr/local/opt/openssl@1.1/lib -L/usr/local/opt/readline/lib -L. -fstack-protector-strong -L/usr/local/lib -L/usr/local/opt/libyaml/lib -L/usr/local/opt/openssl@1.1/lib -L/usr/local/opt/readline/lib     -lruby.2.7   &quot;
  In file included from conftest.c:1:
  In file included from /usr/local/Cellar/ruby/2.7.1_2/include/ruby-2.7.0/ruby.h:33:
  In file included from /usr/local/Cellar/ruby/2.7.1_2/include/ruby-2.7.0/ruby/ruby.h:29:
  /usr/local/Cellar/ruby/2.7.1_2/include/ruby-2.7.0/ruby/defines.h:126:10: fatal error: 'stdio.h' file not found
  #include &lt;stdio.h&gt;
           ^~~~~~~~~
  1 error generated.
  checked program was:
  /* begin */
  1: #include &quot;ruby.h&quot;
  2: 
  3: int main(int argc, char **argv)
  4: {
  5:   return !!argv[argc];
  6: }
  /* end */
  
  
  </code></pre>
  <p>and running</p>
  <pre><code>brew install libffi
  </code></pre>
  <p>gives:</p>
  <pre><code>% brew install libffi
  Warning: libffi 3.3 is already installed and up-to-date
  To reinstall 3.3, run `brew reinstall libffi`
  
  </code></pre>
  <p>How to fix this?</p>
  <p>And when I install cocoapods using brew, I get:</p>
  <pre><code>Warning: cocoapods 1.9.3 is already installed and up-to-date
  To reinstall 1.9.3, run `brew reinstall cocoa-pods
  </code></pre>
  <p>Yet when I do:</p>
  <pre><code>pod --version
  </code></pre>
  <p>I get:</p>
  <pre><code>pod --version
  /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/universal-darwin19/rbconfig.rb:229: warning: Insecure world writable dir /Users/prikshetsharma/Library in PATH, mode 040777
  Traceback (most recent call last):
      2: from /usr/local/bin/pod:23:in `&lt;main&gt;'
      1: from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems.rb:302:in `activate_bin_path'
  /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems.rb:283:in `find_spec_for_exe': can't find gem cocoapods (&gt;= 0.a) with executable pod (Gem::GemNotFoundException)
  </code></pre>
  <p>When I run the pod command, it wants to find the gem, and not the pod installed using brew.</p>
  <p>-- EDIT --</p>
  <p>The brew config</p>
  <pre><code>HOMEBREW_VERSION: 2.4.3
  ORIGIN: https://github.com/Homebrew/brew
  HEAD: c69d97aaa5ba07e8c2af3708c8093ca0875cfb06
  Last commit: 3 days ago
  Core tap ORIGIN: https://github.com/Homebrew/homebrew-core
  Core tap HEAD: 2820accc9a0486a8d5f0766bcf01fb560b9d3f9f
  Core tap last commit: 14 hours ago
  HOMEBREW_PREFIX: /usr/local
  HOMEBREW_MAKE_JOBS: 16
  CPU: 16-core 64-bit kabylake
  Homebrew Ruby: 2.6.3 =&gt; /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/ruby
  Clang: 11.0 build 1103
  Git: 2.24.3 =&gt; /Applications/Xcode.app/Contents/Developer/usr/bin/git
  Curl: 7.64.1 =&gt; /usr/bin/curl
  Java: 1.8.0_241
  macOS: 10.15.5-x86_64
  CLT: 11.5.0.0.1.1588476445
  Xcode: 11.5
  
  </code></pre>