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

Calculating dependencies ... done!
Dependency resolution took 1.53 s (backtrack: 0/20).

[ebuild     U  ] dev-util/spirv-headers-1.4.357.0::gentoo [1.4.341.0::gentoo] 559 KiB
[ebuild     U  ] dev-util/spirv-tools-1.4.357.0::gentoo [1.4.341.0::gentoo] USE="-test" 3436 KiB

Total: 2 packages (2 upgrades), Size of downloads: 3995 KiB