all: initial support for freebsd

- Use `copy_file_range(2)` over `sendfile(2)` which has wider
compatibility.
- Special case pam on freebsd and document `configDirectory`
incompatibility.
- Disable jemalloc for FreeBSD by default as it is the system allocator.
- Disable breakpad by default on FreeBSD as breakpad is not supported.

CMakeLists.txt

@@ -44,8 +44,13 @@ boption(BUILD_TESTING "Build tests (dev)" OFF)
 boption(ASAN "ASAN (dev)" OFF) # note: better output with gcc than clang
 boption(FRAME_POINTERS "Keep Frame Pointers (dev)" ${ASAN})
 
-boption(CRASH_REPORTER "Crash Handling" ON)
-boption(USE_JEMALLOC "Use jemalloc" ON)
+if (CMAKE_SYSTEM_NAME STREQUAL "FreeBSD")
+	boption(CRASH_REPORTER "Crash Handling" OFF)
+	boption(USE_JEMALLOC "Use jemalloc" OFF)
+else()
+	boption(CRASH_REPORTER "Crash Handling" ON)
+	boption(USE_JEMALLOC "Use jemalloc" ON)
+endif()
 boption(SOCKETS "Unix Sockets" ON)
 boption(WAYLAND "Wayland" ON)
 boption(WAYLAND_WLR_LAYERSHELL "  Wlroots Layer-Shell" ON REQUIRES WAYLAND)