strip: x86_64-pc-linux-gnu-strip --strip-unneeded -R .comment usr/bin/openal-info usr/lib/libopenal.so.1.6.372 Files matching a file type that is not allowed: usr/lib/libopenal.so.1.6.372
Created attachment 185608 [details] build.log
Created attachment 185610 [details] emerge --info
Created attachment 186560 [details, diff] openal-multilib.patch This makes it install into the correct libdir.
Created attachment 186882 [details, diff] openal-pkgconfig.patch This patch is also necessary. multilib-strict doesn't complain about this, but pkgconfig files should be installed in /usr/$(get_libdir)/pkgconfig, not in /usr/lib/pkgconfig.
Your pkgconfig patch has already been applied upstream, added with a better multilib patch (also sent upstream) directly against the cmake file.