Improve HTML rendering performance #994

Job	Run time
Run consistency checks on the spec and XML sources	51s
Build the core-only spec, to try and catch ifdef errors in extension markup	51s
Verify repository license compliance	39s
Run Vulkan CTS framework tests to validate against XML changes	1m 36s
Build the vulkan specification and generate any associated files (such as vulkan.h)	7m 3s
Build a test spec and check against expectation, to make sure the spec toolchain works as expected	1m 14s
Generate Rust bindings (Ash crate)	44s
Compile a simple test program that uses vulkan.h	12s
Generate the vulkan C++ header (vulkan.hpp)	1m 9s
Build-test Rust bindings (Ash crate)	43s
Compile a simple test program that uses vulkan.hpp	20s
	15m 22s

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