Check for multiple host architectures in CMake

[masterleinad]

Fixes #4964. For Makefile.kokkos we already have

kokkos/Makefile.kokkos

Lines 461 to 470 in 14bdcee

	# Incompatible flags?
	KOKKOS_INTERNAL_USE_ARCH_MULTIHOST := $(strip $(shell echo "$(KOKKOS_INTERNAL_USE_ARCH_SSE42)+$(KOKKOS_INTERNAL_USE_ARCH_AVX)+$(KOKKOS_INTERNAL_USE_ARCH_AVX2)+$(KOKKOS_INTERNAL_USE_ARCH_AVX512MIC)+$(KOKKOS_INTERNAL_USE_ARCH_AVX512XEON)+$(KOKKOS_INTERNAL_USE_ARCH_KNC)+$(KOKKOS_INTERNAL_USE_ARCH_IBM)+$(KOKKOS_INTERNAL_USE_ARCH_ARM)>1") | bc)
	KOKKOS_INTERNAL_USE_ARCH_MULTIGPU := $(strip $(shell echo "$(KOKKOS_INTERNAL_USE_ARCH_NVIDIA)>1") | bc)
	ifeq ($(KOKKOS_INTERNAL_USE_ARCH_MULTIHOST), 1)
	$(error Defined Multiple Host architectures: KOKKOS_ARCH=$(KOKKOS_ARCH) )
	endif
	ifeq ($(KOKKOS_INTERNAL_USE_ARCH_MULTIGPU), 1)
	$(error Defined Multiple GPU architectures: KOKKOS_ARCH=$(KOKKOS_ARCH) )
	endif

that detects if multiple architectures are specified.

[dalg24]

Not a big fain of the macro name but I don't have a better idea

[masterleinad]

SYCL CI is failing in KokkosCore_PerfTestExec. We see this (spurious) failure from time to time.

[nmm0]

Looks good to me. I wish we wouldn't have to mess up the cache when changing host architectures like on multi arch host systems, but the solution to that would be a bit more complicated.

[nmm0]

I would rename this to make it clearer that this also declares the option since it's easily missed

Maybe something like DECLARE_AND_CHECK_HOST_ARCH though that's kinda verbose