These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 2.15 s (backtrack: 4/20).

[ebuild  N     ] dev-util/vulkan-headers-1.4.357.0::gentoo  USE="-test" 3298 KiB
[ebuild     U  ] dev-util/spirv-headers-1.4.357.0::gentoo [1.4.341.0::gentoo] 559 KiB
[ebuild  N     ] media-libs/vulkan-loader-1.4.357.0::gentoo  USE="X -wayland" 1779 KiB
[ebuild  N     ] app-arch/lz4-1.10.0-r1:0/1.10.0-meson::gentoo  USE="-static-libs -test" 379 KiB
[ebuild  N     ] dev-debug/gfxreconstruct-1.4.357.0::gentoo  USE="X -wayland" 61005 KiB

Total: 5 packages (1 upgrade, 4 new), Size of downloads: 67017 KiB

WARNING: One or more updates/rebuilds have been skipped due to a dependency conflict:

dev-util/vulkan-headers:0

  (dev-util/vulkan-headers-1.4.363.0:0/0::gentoo, ebuild scheduled for merge) USE="-test" conflicts with
    ~dev-util/vulkan-headers-1.4.357.0 required by (dev-debug/gfxreconstruct-1.4.357.0:0/0::gentoo, ebuild scheduled for merge) USE="X -wayland"
    ^                        ^^^^^^^^^


!!! The following update(s) have been skipped due to unsatisfied dependencies
!!! triggered by backtracking:

media-libs/vulkan-loader:0