Ebuild
└─ Dependencies

To figure out what a binary depends on, you can either

• Run scanelf -n <program>
• Run objdump -p <program> | grep NEEDED
• Read QA messages made during the build of an ebuild
• Run ldd <program>

Note that ldd will show more runtime dependencies than strictly needed in an ebuild.

Use equery belongs to figure out which package the shared library object comes from.