Fix test helper: runCommand

[TWiStErRob]

net.twisterrob.gradle/plugin/base/src/testFixtures/kotlin/net/twisterrob/test/process/index.kt

Lines 27 to 39 in cf75d81

	.apply { waitFor(timeout, MILLISECONDS) }
	.also { process ->
	if (verifyError && process.exitValue() != 0) {
	val out = process.inputStream.bufferedReader().readText()
	val err = process.errorStream.bufferedReader().readText()
	assertEquals(
	0, process.exitValue(),
	@Suppress("StringShouldBeRawString") // It would be more complex that way.
	"Non-zero exit value:\nstdout:\n${out}\nstderr:\n${err}"
	)
	}
	}
	.run { inputStream.bufferedReader().readText() }

val out = StringWriter(); thread { process.inputStream.reader().copyTo(out) }

See https://stackoverflow.com/a/3285479/253468 and TWiStErRob/net.twisterrob.inventory#359

also assert waitFor return value.