MLIR on armv7


I have been testing the llvm release (11.0.0 - rc1) on armv7 as I often do, and I noticed that MLIR is now enabled by default. Furthermore, there are lots of test failures.

I would like to disable building MLIR for armv7, at least for this release. Is there interest in supporting it in the future? It seems 32-bit support in general doesn’t exist. If anyone is willing to maintain it, we (Linaro) can add MLIR to our armv7 buildbots and to the release and report any issues that we find. Unfortunately at the moment we don’t have the bandwidth to actively solve these issues ourselves.