When compiling media-plugins/gst-plugins-vorbis-0.10.24, I got the error:
grep: /usr/lib/libogg.la: No such file or directory
/bin/sed: can't read /usr/lib/libogg.la: No such file or directory
libtool: link: `/usr/lib/libogg.la' is not a valid libtool archive
I fixed it by removing the line that deletes all .la files in the libogg ebuild on my system, and rebuilding that.
According to http://wiki.archlinux.org/index.php/Libtool_slaying it's because a dependency in between didn't delete its .la files. In that case the offender would be libvorbis (all versions in my current tree). I haven't tested this yet, as I'm in the middle of a sizeable update.
Steps to Reproduce:
1. emerge media-plugins/gst-plugins-vorbis-0.10.24
2. watch it fail
*** This bug has been marked as a duplicate of bug 275597 ***