[llvm] [SPIRV] Change how to detect OpenCL/Vulkan Env and update tests accordingly. (PR #129689)

[Nathan Gauër via llvm-commits]

Keenuts wrote:

> @Keenuts friendly ping

Sorry, missed your notification
You mean we have tests using `spirv-unknown-unknown` for Vulkan? If so, yes I don't see any issues with updating those to have the explicit `vulkan` env bit


https://github.com/llvm/llvm-project/pull/129689