Fix some issues with VK_EXT_device_generated_commands proposal #970

Job	Run time
Build the core-only spec, to try and catch ifdef errors in extension markup	51s
Verify repository license compliance	39s
Build the vulkan specification and generate any associated files (such as vulkan.h)	6m 12s
Run Vulkan CTS framework tests to validate against XML changes	1m 44s
Build a test spec and check against expectation, to make sure the spec toolchain works as expected	1m 22s
Run various checker scripts on the spec and XML sources	54s
Compile a simple test program that uses vulkan.h	7s
Generate Rust bindings (Ash crate)	37s
Generate the vulkan C++ header (vulkan.hpp)	1m 2s
Build-test Rust bindings (Ash crate)	36s
Compile a simple test program that uses vulkan.hpp	19s
	14m 23s

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