`_CopyMissingUncooked` and shaders

[Xymanek]

X2ModBuildCommon/build_common.ps1

Lines 145 to 147 in b339358

	# Do this last as there is no need for it earlier - the cooker obviously has access to the game assets
	# and precompiling shaders seems to do nothing (I assume they are included in the game's GlobalShaderCache)
	$this._PerformStep({ ($_)._CopyMissingUncooked() }, "Copying", "Copied", "requested uncooked packages")

I wrote that comment before I knew about seekfree shader cache (which is inlined into each SF package). We should verify that the current setup isn't causing runtime shader compilations