adding minor details to the readme

README.md

@@ -6,16 +6,23 @@ Requirements:
 - `julia` in your path, **must be** 1.6.
 - a repository with `scipoptsuite` to test.
 
-Basic usage:
+**Basic usage:**
 ```
 ./run_builder.sh path_to_scipoptsuite
 ```
 
-Advanced usage:
+if BinaryBuilder is not used yet, please set the following env variable before running
+```
+export BINARYBUILDER_AUTOMATIC_APPLE = true 
+```
+Note: using the scipoptsuite git repository requires an account of the RWTH Aachen or disabling GCG with `-DGCG=off`
+
+**Advanced usage:**
 - Change the SCIP build script with the `script` variable of the Julia `build.jl` program
 - If you want to drop into the build environment when an error occurs, use the `debug` flag:
 
 ```bash
+export SCIPOPTSUITE=path_to_scipoptsuite
 julia --project builder.jl --deploy=local --verbose --debug
 ```