Usage of Gradle option "--parallel" should be safe

Usage of Gradle option "--parallel" should be safe

Gradle should not execute several "yarn install" in parallel,
because Yarn doesn't support concurrent access to its global cache.

"task1.mustRunAfter(task2)" ordering has an effect only when both
tasks are scheduled for execution, however currently task
":private:docs:yarn" is not executed during execution of "gradle build".
Therefore "mustRunAfter" should be established between all pairs of
"yarn install" tasks to define their total order and to prevent their
concurrent execution even in case when one or more of these tasks not
scheduled.