title: was a library built with libc++ or libstdc++ on Mac
body: <p>How can I tell if a library has been built with libc++ or libstdc++ on mac?</p>
  
  <p>I have been using otool -L, but this does not seem to show it (mac has no ldd)</p>
  
  <p>If i have library X, I want to know if I have to rebuild it as I move from GCC to clang. I have built a number of libraries with GCC, mac libraries are generally built with clang AFAIK.</p>