DOC: Extended previous commit.

doc/README_SETUP.md

@@ -6,7 +6,7 @@
 
 ## Build
 
-We use [cmake](https://cmake.org) as build tool.
+We use [cmake](https://cmake.org) as build tool and assume gcc as compiler.
 
 0. clone/update the subrepo `git submodule update --init proto`
 1. `mkdir build && cd build`
@@ -25,7 +25,7 @@ command (3.).
 
 ### How to build on MacOS
 
-Instead of the above conan command (2.) use
+If you use apple-clang as the compiler: Instead of the above conan command (2.) use
 
 2. `conan install .. -s "compiler.cppstd=17"`
 
@@ -88,7 +88,8 @@ standard manually by `conan install .. [other options] -s
 For the tests there is a slightly different setup required (with option `-D CMAKE_BUILD_TYPE=Debug`)
 
 1. `mkdir build && cd build/`
-2. `conan install .. ` (with gcc, append ` -s "compiler.libcxx=libstdc++11"`, with apple-clang, append ` -s compiler.cppstd=17`)
+2. `conan install .. ` (with gcc, append ` -s "compiler.libcxx=libstdc++11"`, with apple-clang,
+   append ` -s compiler.cppstd=17`)
 3. `cmake -B . -D CMAKE_BUILD_TYPE=Debug ..`
    * If your clang-format version is too old, formatting, linting etc. can be skipped:
 	 `cmake -B . -D CMAKE_BUILD_TYPE=Debug -D SKIP_LINTING=ON ..`