Installing android sdk on custom project

General
1
  1. License Acceptance: The build process is failing because the Android SDK license has not been accepted. This is a requirement for using the Android SDK in your development environment.
  2. Error Location: The error occurs while evaluating the ‘packages’ attribute in your Nix configuration, specifically when trying to include the Android SDK.
   January 16, 2019

   You must accept the following licenses:
     - android-sdk-license

   a)
     by setting nixpkgs config option 'android_sdk.accept_license = true;'.
   b)
     by an environment variable for a single invocation of the nix tools.
       $ export NIXPKGS_ACCEPT_ANDROID_SDK_LICENSE=1

while building i get this error
i believe i will have to accept the licenses while building itself but no use