title: Adding header files to the C++ library recursively from an external library
body: <p>I'm trying to use an external library in my current C++ project. The header files in the library are in multiple folders and I need to add them into my make file (using cmake). I can add the header files by declaring each folder separately and ask the make file to find all header files in the folder. But is there a way to add all the headers inside multiple folders in one line of code?
  Here's my cmake code for adding the headers in separate folders:</p>
  
  <pre><code>FILE (GLOB LibraryFolderOneHeaders ExternalLibrary/ExternalLibraryFolderOne/*.h)
  FILE (GLOB LibraryFolderTwoHeaders ExternalLibrary/ExternalLibraryFolderTwo/*.h)
  
  SOURCE_GROUP("Header Files\\LibraryFolderOne" FILES ${LibraryFolderOneHeaders})
  SOURCE_GROUP("Header Files\\LibraryFolderTwo" FILES ${LibraryFolderTwoHeaders })
  ...
  </code></pre>
  
  <p>For all the folders.
  Is there a way to find header files all at once?</p>
  
  <p>Thanks</p>