[cmake] Apparently cmake_system_processor is not defined on rpi 32 bit #442

Job	Run time
Debian (bookworm, clang, clang++, clang)	28m 8s
Debian (bookworm, clang-15, clang++-15, clang-15)	27m 18s
Debian (bookworm, gcc, g++, build-essential)	33m 54s
Debian (trixie, gcc, g++, build-essential)	31m 51s
Debian (trixie, clang, clang++, clang)	29m 41s
Debian (trixie, gcc-14, g++-14, gcc-14 g++-14)	1h 2m 44s
Debian (trixie, clang-17, clang++-17, clang-17)	30m 24s
	4h 4m 0s

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