[Util] add helper function to get FINN root

run-docker.sh

@@ -97,5 +97,6 @@ docker run -t --rm --name $DOCKER_INST_NAME -it \
 -v $VIVADO_PATH:$VIVADO_PATH \
 -e VIVADO_PATH=$VIVADO_PATH \
 -e FINN_INST_NAME=$DOCKER_INST_NAME \
+-e FINN_ROOT="/workspace/finn" \
 -p $JUPYTER_PORT:$JUPYTER_PORT \
 $DOCKER_TAG bash -c "$DOCKER_CMD"

src/finn/util/basic.py

@@ -10,6 +10,19 @@ import onnx
 from finn.core.datatype import DataType
 
 
+def get_finn_root():
+    "Return the root directory that FINN is cloned into."
+
+    try:
+        return os.environ["FINN_ROOT"]
+    except KeyError:
+        raise Exception(
+            """Environment variable FINN_ROOT must be set
+        correctly. Please ensure you have launched the Docker contaier correctly.
+        """
+        )
+
+
 def make_build_dir(prefix=""):
     """Creates a temporary folder with given prefix to be used as a build dir.
     Use this function instead of tempfile.mkdtemp to ensure any generated files