task completion fails with v7.5 samples (and a workaround)

[errael]

The v7.5 samples do not have a build.gradle file in the root project directory. Completion's __gradle-set-build-file() depends primarily on finding that file in the root project dir.

In the root, doing

$ touch build.gradle

which creates an empty build.gradle file, got completion to start working.

BTW, trying

rootProject.buildFileName = 'lib/build.gradle'

Fails with Multiple projects in this build have build file