DOC: Add build instructions for Mac OS

README_SETUP.md

@@ -9,6 +9,26 @@ We use [cmake](https://cmake.org) as build tool.
 3. `cmake -B . ..`
 4. `cmake --build .`
 
+You may also want to install libcaosdb system-wide to
+`CMAKE_INSTALL_PREFIX/lib` by
+
+5. `cmake --install .`
+
+The default install prefix is `~/.local`. It can be set by adding
+`-DCMAKE_INSTALL_PREFIX=/path/to/install/prefix` to the first cmake
+command (3.).
+
+### How to build on MacOS
+
+Instead of the above conan command (2.) use
+
+2. `conan install .. -s "cppstd=11"`
+
+and continue as you would when building on a Linux system. You may
+have to add `build/lib/` (or, alternatively after installation,
+`CMAKE_INSTALL_PREFIX/lib`) to your `DYLD_LIBRARY_PATH` environmental
+variable.
+
 ## Unit Tests
 
 ### Build