Tests don't work on M1 Mac

[tetsuo-cpp]

The CMake configuration allows testing on x86 for anything that's not Windows. However for ARM, it only supports Linux. Relevant snippet here.

If I hack up the CMake to build on my M1 anyway, I see this assembler error on ninja test_dependencies.

/var/folders/mq/25w5gx6x0w7c5hq2l6tz8k_40000gn/T/Tests-070b22.s:7477:4: error: this directive must appear between .cfi_startproc and .cfi_endproc directives
7: .cfi_endproc ; .section "__aarch64_test_table", "a" ; .quad 0 ; hlt #0 ;