Gentoo's Bugzilla –
Attachment 578034 Details for
Bug 686984dev-util/electron-2.0.17-r1 - ninja: error: '.../work/electron-2.0.17/chromium/out/Release/clang_x64_v8_arm64/mksnapshot', needed by 'static_library/mksnapshot', missing and no known rule to make it