title: troubles when I use homebrew
body: <p>I want to install git in my Mac(OS X 10.10.3).I write: brew install git</p>
  
  <p>but it reported :</p>
  
  <pre><code>sh: line 1:  1549 Abort trap: 6           /Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -sdk / -find clang 2&gt; /dev/null
  clang: error: unable to find utility "clang", not a developer tool or in PATH
  sh: line 1:  1552 Abort trap: 6           /Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -sdk / -find otool 2&gt; /dev/null
  otool: error: unable to find utility "otool", not a developer tool or in PATH
  Error: Failure while executing: /usr/bin/otool -L /usr/bin/install_name_tool
  </code></pre>
  
  <p>then I write brew doctor. it reported:</p>
  
  <pre><code>Warning: /usr/local/include isn't writable.
  
  This can happen if you "sudo make install" software that isn't managed by
  by Homebrew. If a formula tries to write a file to this directory, the
  install will fail during the link step.
  
  You should probably `chown` /usr/local/include
  
  Warning: /usr/local/lib isn't writable.
  
  This can happen if you "sudo make install" software that isn't managed by
  by Homebrew. If a formula tries to write a file to this directory, the
  install will fail during the link step.
  
  You should probably `chown` /usr/local/lib
  sh: line 1:  1318 Abort trap: 6           /Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -sdk / -find otool 2&gt; /dev/null
  otool: error: unable to find utility "otool", not a developer tool or in PATH
  Error: Failure while executing: /usr/bin/otool -L /usr/bin/install_name_tool
  </code></pre>
  
  <p>then I chown the lib and include with "sudo chown 755 include""sudo chown 755 lib"
  the first and second warning are removed but the third is still there.</p>
  
  <p>And what confused me more is that in my finder:/usr/local/ the "include" and "lib" which should be folders but become files.
      how can I slove the error "cannot find otool" and install git with brew and </p>
  
  <p>why my lib and include folder become files?... thanks for your help!</p>