[mlir] [mlir] tentative fix for "'GTEST_NO_LLVM_SUPPORT' is not defined" war… (PR #84539)

[Ingo Müller]

ingomueller-net wrote:

I guess that this should silence the warnings for MLIR. I am not sure whether this shouldn't even be set at a higher level, maybe for all of LLVM. The question that I am not able to answer is what is the right default value? Some projects set the value to 1 and the whole purpose of the macro seems to be interoperability with LLVM. Doesn't this mean that the same value should be used for all of LLVM?

https://github.com/llvm/llvm-project/pull/84539