Can't install on Haiku R1 beta 4

[realtaraharris]

mimalloc builds just fine, but it appears that there's something wrong with the default install path. Or am I doing something wrong?

~/mimalloc/build> make install
[ 40%] Built target mimalloc
[ 81%] Built target mimalloc-static
[ 83%] Built target mimalloc-obj
[ 89%] Built target mimalloc-test-api
[ 94%] Built target mimalloc-test-api-fill
[100%] Built target mimalloc-test-stress
Install the project...
-- Install configuration: "Release"
-- Installing: /boot/system/lib/libmimalloc.so.2.0
CMake Error at cmake_install.cmake:52 (file):
  file INSTALL cannot copy file
  "/boot/home/mimalloc/build/libmimalloc.so.2.0" to
  "/boot/system/lib/libmimalloc.so.2.0": Read-only file system.