[FEA] Enable CACHE for LLVM_GIT_REPO and LLVM_BUILD_COMMIT_HASH.

[Peter9606]

Hi,

cuda-tile/cmake/IncludeLLVM.cmake

Lines 26 to 27 in 8a77569

	set(LLVM_GIT_REPO "https://github.com/llvm/llvm-project.git")
	set(LLVM_BUILD_COMMIT_HASH 3d7018c70b97e6a3d6dfe08e9f11dede96242d1f)

It would be more convenient to enable CACHE for these two macros.

Regards,
Peter Han