Do not set RPATH on FreeBSD either.
--- CMakeLists.txt.orig	2020-07-15 08:02:19 UTC
+++ CMakeLists.txt
@@ -237,7 +237,7 @@ if(WIN32)
 endif(WIN32)
 
 # rpath handling: use rpath in installed binaries
-if(NOT CMAKE_SYSTEM_NAME MATCHES Linux)
+if(NOT CMAKE_SYSTEM_NAME MATCHES "FreeBSD|Linux")
   set(CMAKE_INSTALL_RPATH ${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR})
   set(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
 endif()