Dont generate baseline if empty

[BraisGabin]

This PR is a rebase from #3027 full credit to @realdadfish

I added a new commit removing the output when the baseline is not generated. We had several PR already making detekt less noisy so I think that we should keep it like this. (Maybe for 2.0 we could implement a log system with different levels so this kind of output can be written at a verbose level).

Merge this PR is safe now. We already merged #3429

[codecov]

Codecov Report

Merging #3450 (713dcab) into master (623e7fd) will decrease coverage by 0.00%.
The diff coverage is 70.00%.

@@             Coverage Diff              @@
##             master    #3450      +/-   ##
============================================
- Coverage     80.28%   80.27%   -0.01%     
- Complexity     2784     2786       +2     
============================================
  Files           454      454              
  Lines          8415     8416       +1     
  Branches       1608     1609       +1     
============================================
  Hits           6756     6756              
  Misses          789      789              
- Partials        870      871       +1     

Impacted Files	Coverage Δ	Complexity Δ
.../arturbosch/detekt/core/baseline/BaselineFacade.kt	77.77% <0.00%> (ø)	6.00 <2.00> (ø)
...osch/detekt/core/baseline/BaselineResultMapping.kt	73.33% <77.77%> (-5.24%)	8.00 <3.00> (+2.00)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 623e7fd...49364af. Read the comment docs.