Azure Devops or General: Can't install NDK version on the fly, as directory is not writable

[carstenhag]

The NDK version I am using in my project is different to the one provided by the current images (see #128).
At the default Azure DevOps / GitHub images, NDK versions that aren't installed get automatically installed by Gradle. With this image, it doesn't seem to work.

Not sure if this can be fixed by this docker image though :D

> Configure project :app
Checking the license for package NDK (Side by side) 26.2.11394342 in /opt/android/sdk/licenses
License for package NDK (Side by side) 26.2.11394342 accepted.
Preparing "Install NDK (Side by side) 26.2.11394342 v.26.2.11394342".
Warning: Failed to read or create install properties file.

FAILURE: Build completed with 2 failures.

1: Task failed with an exception.
-----------
* What went wrong:
A problem occurred configuring project ':app'.
> com.android.builder.sdk.InstallFailedException: Failed to install the following SDK components:
      ndk;26.2.11394342 NDK (Side by side) 26.2.11394342
  The SDK directory is not writable (/opt/android/sdk)