BCV tasks do not work for a project with generated sources when configuration cache is enabled

[fzhinkin]

While debugging #206 I found that all BCV tasks checking that a project has some non-empty source sets (it's almost all tasks) don't work if a project has generated sources only and the configuration cache is turned on.

The only workaround for the problem is to disable the configuration cache.

[shanshin]

Issue was fixed, tests: https://github.com/Kotlin/binary-compatibility-validator/pull/210/files#diff-a8a430c63b2e5c4fae5862f190d9f7352dbc058b2415fb2d36923b0cca1e0d11