CMake: don't unconditionally compile Segment.{h,c} (#516) #948

Job	Run time
Amalgamated build (Ubuntu 22.04)	5s
fuzzing (address)	11m 27s
CMake build + tests (macOS-latest )	13s
fuzzing (undefined)	11m 25s
CMake build + tests (macOS-latest -DZYAN_NO_LIBC=ON)	11s
fuzzing (memory)	11m 27s
MSBuild build (windows-2022)	1m 51s
CMake build + tests (windows-2022 )	1m 20s
CMake build + tests (windows-2022 -DZYAN_NO_LIBC=ON)	34s
CMake build + tests (ubuntu-22.04 )	9s
CMake build + tests (ubuntu-22.04 -DZYAN_NO_LIBC=ON)	6s
CMake build + tests (ubuntu-22.04 -DZYDIS_MINIMAL_MODE=ON -DZYDIS_FEATURE_ENCODER=OFF)	8s
CMake build + tests (windows-2022 -TClangCL)	2m 31s
	41m 27s

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