Fix macOS `cmake --install` command failing due to `Read-only file sy… #360

Job	Run time
freebsd12 (CMake) (LLVM)	5m 52s
freebsd12 (CMake) (LLVM)	5m 52s
debian:12 (Latest Mapnik) (CMake) (GNU)	2m 3s
debian:12 (Latest Mapnik) (CMake) (GNU)	2m 3s
freebsd13 (CMake) (LLVM)	5m 53s
freebsd13 (CMake) (LLVM)	5m 53s
centos:7 (CMake) (GNU)	3m 46s
centos:7 (CMake) (GNU)	3m 46s
ubuntu:22.04 (Latest Mapnik) (CMake) (GNU)	2m 26s
ubuntu:22.04 (Latest Mapnik) (CMake) (GNU)	2m 26s
freebsd14 (CMake) (LLVM)	5m 26s
freebsd14 (CMake) (LLVM)	5m 26s
debian:11 (CMake) (GNU)	1m 50s
debian:11 (CMake) (GNU)	1m 50s
debian:12 (CMake) (GNU)	1m 43s
debian:12 (CMake) (GNU)	1m 43s
macos-12 (CMake) (LLVM)	9m 34s
macos-12 (CMake) (LLVM)	9m 34s
debian:testing (CMake) (GNU)	1m 48s
debian:testing (CMake) (GNU)	1m 48s
macos-13 (Autotools) (LLVM)	13m 34s
macos-13 (Autotools) (LLVM)	13m 34s
fedora:38 (CMake) (GNU)	3m 22s
fedora:38 (CMake) (GNU)	3m 22s
macos-13 (CMake) (LLVM)	15m 35s
macos-13 (CMake) (LLVM)	9m 14s
fedora:39 (CMake) (GNU)	2m 28s
fedora:39 (CMake) (GNU)	2m 28s
fedora:rawhide (CMake) (GNU)	2m 33s
fedora:rawhide (CMake) (GNU)	2m 33s
opensuse/leap:15 (CMake) (GNU)	5m 14s
opensuse/leap:15 (CMake) (GNU)	5m 14s
ubuntu:20.04 (CMake) (GNU)	1m 42s
ubuntu:20.04 (CMake) (GNU)	1m 42s
ubuntu:rolling (CMake) (GNU)	2m 2s
ubuntu:rolling (CMake) (GNU)	2m 2s
ubuntu:22.04 (Autotools) (GNU)	1m 58s
ubuntu:22.04 (Autotools) (GNU)	1m 58s
ubuntu:22.04 (Autotools) (LLVM)	2m 3s
ubuntu:22.04 (Autotools) (LLVM)	2m 3s
ubuntu:22.04 (CMake) (GNU)	1m 32s
ubuntu:22.04 (CMake) (GNU)	1m 32s
ubuntu:22.04 (CMake) (LLVM)	1m 50s
ubuntu:22.04 (CMake) (LLVM)	1m 50s
	3h 2m 7s

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