title: Including headers in an Xcode 4.2.1 project
body: <p>I'm trying to use a library, specifically SOIL (Simple OpenGL Image Library) in Xcode 4.2.1. Under Build Phases -> Link Library with Libraries I add all the .h and .c files that came with the SOIL zip archive. </p>
  
  <p>When I build the project, I get the following error message for every .h and .c file added:</p>
  
  <blockquote>
    <p>warning: skipping file '/Users/saw/XcodeProjects/Assignment01 copy/Assignment01/image_DXT.c' 
    (unexpected file type 'sourcecode.c.c' in Frameworks &amp; Libraries build phase)</p>
  </blockquote>
  
  <p>and a linker error:</p>
  
  <blockquote>
    <p>"_SOIL_load_OGL_texture", referenced from: Init() in main.o Symbol(s)
    not found for architecture x86_64 Clang: error: linker command failed
    with exit code 1 (use -v to see invocation)</p>
  </blockquote>