Be more specific for nvm and flask

Author: mxmeinhold

.devcontainer/devcontainer.json

@@ -53,7 +53,7 @@
 	// "oryx build" will automatically install your dependencies and attempt to build your project
   "postCreateCommand": [
     "pip install --progress-bar=off install -r requirements.txt;",
-    "$NVM_DIR/nvm.sh && nvm install && nvm use && npm install -g gulp && yarn install && gulp production;",
-    "flask db upgrade;"
+    "source $NVM_DIR/nvm.sh && nvm install && nvm use && npm install -g gulp && yarn install && gulp production;",
+    "/home/codespace/.local/bin/flask db upgrade;"
   ]
 }