-DUSE_EDITLINE is passed, but editline isn't pulled in as a dependency.
It's using libedit rather than editline, and if not found it auto-disables the cli debugger so it's indeed missing.
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=c18a9fed6c1b20240997b5f655902c0223073552 commit c18a9fed6c1b20240997b5f655902c0223073552 Author: Lars Wendler <polynomial-c@gentoo.org> AuthorDate: 2021-04-19 21:16:45 +0000 Commit: Lars Wendler <polynomial-c@gentoo.org> CommitDate: 2021-04-19 21:18:21 +0000 games-emulation/mgba: USE="debug" requires dev-libs/libedit Closes: https://bugs.gentoo.org/769647 Signed-off-by: Lars Wendler <polynomial-c@gentoo.org> games-emulation/mgba/{mgba-0.8.4.ebuild => mgba-0.8.4-r1.ebuild} | 1 + games-emulation/mgba/{mgba-0.9.1.ebuild => mgba-0.9.1-r1.ebuild} | 1 + games-emulation/mgba/mgba-9999.ebuild | 3 ++- 3 files changed, 4 insertions(+), 1 deletion(-)