!!! The ebuild selected to satisfy "dev-libs/libclc" has unmet requirements.
- dev-libs/libclc-0.2.0_pre20191024::gentoo USE="" ABI_X86="(64)" VIDEO_CARDS="-nvidia -r600 -radeonsi"

  The following REQUIRED_USE flag constraints are unsatisfied:
    any-of ( video_cards_nvidia video_cards_r600 video_cards_radeonsi )

(dependency required by "media-libs/mesa-20.0.8::gentoo[gallium,opencl]" [ebuild])
(dependency required by "mesa" [argument])