Why cmake doesn't create a links for some versioned dylibs

explanation.txt

    # When Cmake is told the avidemux2_cli target has a target_link_library
    # dependency on the versioned ffmpeg lib it just built as a seperate
    # library, libADM5avcodec.52.dylib, cmake then does not link against
    # that versioned lib. It links against the unversioned lib.  Not only
    # does it link against the unversioned lib, but it only installs the
    # the versioned one and doesn't symlink it to an unversioned one because
    # it's not building and installing the library, rather it's building and
    # installing the app.  The ffmpeg build & install (which did create
    # symlinks automatically) is only done into the temporary macbuild
    # folder that avidemux itself is building in.
    # This linking against unversioned libs I think is a feature of cmake.
    # Well I say I think only after a week of pulling these files apart.
    # So here we create symlinks for the unversioned libs, so that
    # avidemux2_cli can load them when you run it after install.
    if ARGV.build_head? then
      ln_sf lib+'libADM5avcodec.53.dylib', lib+'libADM5avcodec.dylib'
      ln_sf lib+'libADM5avformat.53.dylib', lib+'libADM5avformat.dylib'
      ln_sf lib+'libADM5avutil.51.dylib', lib+'libADM5avutil.dylib'
      ln_sf lib+'libADM5postproc.51.dylib', lib+'libADM5postproc.dylib'
      ln_sf lib+'libADM5swscale.2.dylib', lib+'libADM5swscale.dylib'
    else
      ln_sf lib+'libADM5avcodec.52.dylib', lib+'libADM5avcodec.dylib'
      ln_sf lib+'libADM5avformat.52.dylib', lib+'libADM5avformat.dylib'
      ln_sf lib+'libADM5avutil.50.dylib', lib+'libADM5avutil.dylib'
      ln_sf lib+'libADM5postproc.51.dylib', lib+'libADM5postproc.dylib'
      ln_sf lib+'libADM5swscale.0.dylib', lib+'libADM5swscale.dylib'
    end