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

[Nathan Gauër via llvm-commits]

Keenuts wrote:

> @Keenuts @bader @VyacheslavLevytskyy @MrSidims @michalpaszkowski this is ready for review now. Note that this changed significantly since the first time it was open.

Don't know for others, but there is the `re-request review` button which will make this reappear in the https://github.com/pulls/review-requested page (vs a ping which is 1 notification in a ocean of noise) 

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