[libclc] [llvm] [libclc] Enable LLVM_RUNTIME_TARGETS in build system (PR #189892)

[Wenju He via llvm-commits]

wenju-he wrote:

> Is it possible to just do like `ninja -C runtimes/runtimes-amdgcn-amd-amdhsa-llvm-bins check-libclc`?

yes, `ninja -C runtimes/runtimes-amdgcn-amd-amdhsa-llvm-bins check-libclc` works and should behave the same as `ninja check-libclc-amdgcn-amd-amdhsa-llvm`.
`ninja check-libclc-amdgcn-amd-amdhsa-llvm` expands to `cmake --build .../runtimes/runtimes-amdgcn-amd-amdhsa-llvm-bins/ --target check-libclc --config Release`.

https://github.com/llvm/llvm-project/pull/189892