Poor output of `TestSuiteExeMissing`

[mpilgrem]

-- Stack.Build.ExecutePackage.singleTest
logError $
  displayShow $ TestSuiteExeMissing
    package.buildType == C.Simple)
    exeName
    (packageNameString package.name)
    (unqualCompToString testName)

results in output like:

TestSuiteExeMissing False "stack-unit-test.exe" "stack" "stack-unit-test"

For an example, see:

• Add Backpack support to Stack #6865