As the title says, seems some recent change causes Dolphin to not build anymore, owing to a clash with Linux system headers. I couldn't tell you which upstream change caused the issue specifically but seems it's tricked down to Gentoo finally as I located a bug report for Fedora with the same issue which provided a patch to solve the issue, just rename IP_PROTOCOL to something else in Source/Core/Core/HW/EXI/BBA/BuiltIn.cpp/.h and it builds successfully. Shouldn't be much issue to just slip the patch into the tree.
As the title says, seems some recent change causes Dolphin to not build anymore, owing to a clash with Linux system headers. I couldn't tell you which upstream change caused the issue specifically but seems it's tricked down to Gentoo finally as I located a bug report for Fedora with the same issue which provided a patch to solve the issue, just rename IP_PROTOCOL to something else in Source/Core/Core/HW/EXI/BBA/BuiltIn.cpp/.h and it builds successfully. Shouldn't be much issue to just slip the patch into the tree.
Mentioned Fedora bug report and patch https://bugzilla.redhat.com/show_bug.cgi?id=2241350 https://src.fedoraproject.org/rpms/dolphin-emu/blob/42cc2e29740950e22fe027c89bdbb002813e48ca/f/c284580bb0f0c27c4ec1ea16104895ba82533efc.patch
And usual emerge --info, -pqv and failed build log just because: info.txt pqv.txt build.log