Compare ProcessorCount to SystemInformation count. (#11302)

Maximize output to gather data on the dashboards.
Only FATAL_ERROR out once at the bottom if an error
occurred earlier.

Tests/CMakeTests/ProcessorCountTest.cmake.in

@@ -3,11 +3,45 @@ include(ProcessorCount)
 ProcessorCount(processor_count)
 message("processor_count='${processor_count}'")
 
-if(NOT processor_count MATCHES "^[0-9]+$")
-  message(FATAL_ERROR "ProcessorCount function returned a non-integer")
+execute_process(
+  COMMAND "@CMAKE_BINARY_DIR@/Source/kwsys/$ENV{CMAKE_CONFIG_TYPE}/cmsysTestsCxx"
+  testSystemInformation
+  OUTPUT_VARIABLE out)
+string(REGEX REPLACE "(.*)GetNumberOfPhysicalCPU:.([0-9]*)(.*)" "\\2"
+  system_info_processor_count "${out}")
+message("system_info_processor_count='${system_info_processor_count}'")
+
+if(system_info_processor_count EQUAL processor_count)
+  message("processor count matches system information")
 endif()
 
+# Evaluate possible error conditions:
+#
+set(err 0)
+
 if(processor_count EQUAL 0)
-  message(FATAL_ERROR "could not determine number of processors
+  set(err 1)
+  message("could not determine number of processors
 - Additional code for this platform needed in ProcessorCount.cmake?")
 endif()
+
+if(NOT system_info_processor_count EQUAL processor_count)
+  set(err 2)
+  message("SystemInformation and ProcessorCount.cmake disagree:\n"
+    "processor_count='${processor_count}'\n"
+    "SystemInformation processor_count='${system_info_processor_count}'")
+endif()
+
+if(NOT processor_count MATCHES "^[0-9]+$")
+  set(err 3)
+  message("ProcessorCount function returned a non-integer")
+endif()
+
+if(NOT system_info_processor_count MATCHES "^[0-9]+$")
+  set(err 4)
+  message("SystemInformation ProcessorCount function returned a non-integer")
+endif()
+
+if(err)
+  message(FATAL_ERROR "err='${err}'")
+endif()