Simplify argument parsing logic, remove any exitProcess() calls from buildRunner

[arturbosch]

No description provided.

[codecov-io]

Codecov Report

Merging #2260 into master will increase coverage by 0.09%.
The diff coverage is 40%.

@@             Coverage Diff             @@
##             master   #2260      +/-   ##
===========================================
+ Coverage     81.61%   81.7%   +0.09%     
+ Complexity     2120    2118       -2     
===========================================
  Files           349     349              
  Lines          6054    6047       -7     
  Branches       1106    1108       +2     
===========================================
  Hits           4941    4941              
+ Misses          524     517       -7     
  Partials        589     589

Impacted Files	Coverage Δ	Complexity Δ
...tlin/io/gitlab/arturbosch/detekt/generator/Main.kt	0% <0%> (ø)	0 <0> (ø)	⬇️
.../kotlin/io/gitlab/arturbosch/detekt/cli/CliArgs.kt	100% <100%> (ø)	6 <0> (ø)	⬇️
...ain/kotlin/io/gitlab/arturbosch/detekt/cli/Main.kt	36% <33.33%> (-14%)	6 <5> (-1)
...tlin/io/gitlab/arturbosch/detekt/cli/JCommander.kt	62.5% <62.5%> (+62.5%)	0 <0> (ø)	⬇️
...n/kotlin/io/gitlab/arturbosch/detekt/cli/Errors.kt	66.66% <66.66%> (ø)	0 <0> (?)

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