[CI] Spurious test failures

[marcalff]

Very often, the CI on windows fails and returns an non 0 return code to the github worker.

For example:

CMake exporter proto (Build as DLL)

run cmake test (DLL build)
./ci/do_ci.ps1 cmake.dll.test

end with:

Error: Process completed with exit code 1.

Note that the CI runs the example code, as in:

    examples\simple\Debug\example_simple.exe
    $exit = $LASTEXITCODE
    if ($exit -ne 0) {
      exit $exit
    }
    examples\metrics_simple\Debug\metrics_ostream_example.exe
    $exit = $LASTEXITCODE
    if ($exit -ne 0) {
      exit $exit
    }
    examples\logs_simple\Debug\example_logs_simple.exe
    $exit = $LASTEXITCODE
    if ($exit -ne 0) {
      exit $exit
    }

and failures happen after the example code is executed (it prints output visible in the logs).

Root cause:

main() do not return a proper value.

For example in examples/simple/main.cc:

int main()
{
  // Removing this line will leave the default noop TracerProvider in place.
  InitTracer();

  foo_library();

  CleanupTracer();
}