Add IR output verification to sample test

[rorbech]

Just a quick and dirty addition outlining a principle to allow IR output verification

[rorbech]

Hmm. IR output seems to hold machine specific paths.

[cmelchior]

Maybe it is just me, but when using it so far down a call chain, I'm not sure at all what it is? Some entries in a map, but the context is gone

[nhachicha]

@rorbech there's also an AbstractIrGeneratorTestCase used for example in https://github.com/JetBrains/kotlin/blob/master/compiler/tests/org/jetbrains/kotlin/ir/IrJsTextTestCaseGenerated.java which validates the IR against a predefined file https://github.com/JetBrains/kotlin/blob/master/compiler/testData/ir/irJsText/dynamic/dynamicElvisOperator.txt
(corresponding Kotlin file
https://github.com/JetBrains/kotlin/blob/master/compiler/testData/ir/irJsText/dynamic/dynamicElvisOperator.kt)
We could use the same logic as JB for Ir testing ...

[rorbech]

@rorbech there's also an AbstractIrGeneratorTestCase used for example in https://github.com/JetBrains/kotlin/blob/master/compiler/tests/org/jetbrains/kotlin/ir/IrJsTextTestCaseGenerated.java which validates the IR against a predefined file https://github.com/JetBrains/kotlin/blob/master/compiler/testData/ir/irJsText/dynamic/dynamicElvisOperator.txt
(corresponding Kotlin file
https://github.com/JetBrains/kotlin/blob/master/compiler/testData/ir/irJsText/dynamic/dynamicElvisOperator.kt)
We could use the same logic as JB for Ir testing ...

The kotlin infrastructure around this is quite massive and are not (as far as I can see) easily reusable in our context. My take would just be to merge the simple convention about having input, output and expected for each test case and add glue around as needed.