message: fix size_t - int issue
diff: @@ -186,8 +186,8 @@ TEST_P(BPStepsInSituGlobalArrayReaders, EveryStep)
  adios2::Engine reader = ior.Open(fname, adios2::Mode::Read);
  EXPECT_TRUE(reader);
  - size_t stepsWritten = 0;
  - size_t stepsRead = 0;
  + int stepsWritten = 0;
  + int stepsRead = 0;
  for (const auto act : schedule)
  {
  @@ -342,8 +342,8 @@ TEST_P(BPStepsInSituGlobalArrayReaders, NewVarPerStep)
  adios2::Engine reader = ior.Open(fname, adios2::Mode::Read);
  EXPECT_TRUE(reader);
  - size_t stepsWritten = 0;
  - size_t stepsRead = 0;
  + int stepsWritten = 0;
  + int stepsRead = 0;
  for (const auto act : schedule)
  {
  @@ -518,7 +518,7 @@ TEST_P(BPStepsInSituGlobalArrayParameters, EveryOtherStep)
  EXPECT_TRUE(writer);
  auto var_i32 = iow.DefineVariable<int32_t>("i32", shape, start, count);
  EXPECT_TRUE(var_i32);
  - auto var_step = iow.DefineVariable<size_t>("step");
  + auto var_step = iow.DefineVariable<int>("step");
  EXPECT_TRUE(var_step);
  #if ADIOS2_USE_MPI
  @@ -535,10 +535,10 @@ TEST_P(BPStepsInSituGlobalArrayParameters, EveryOtherStep)
  adios2::Engine reader = ior.Open(fname, adios2::Mode::Read);
  EXPECT_TRUE(reader);
  - size_t stepsWritten = 0;
  - size_t stepsRead = 0;
  - size_t varStepsWritten = 0;
  - size_t varStepsRead = 0;
  + int stepsWritten = 0;
  + int stepsRead = 0;
  + int varStepsWritten = 0;
  + int varStepsRead = 0;
  for (const auto act : schedule)
  {
  if (act == Act::Write)
  