message: fixed ISPC detection bug
diff: ## ======================================================================== ##
  # ISPC versions to look for, in decending order (newest first)
  -set(ISPC_VERSION_WORKING "1.12.0" "1.10.0" "1.9.2" "1.9.1")
  +set(ISPC_VERSION_WORKING "1.12.0")
  list(GET ISPC_VERSION_WORKING -1 ISPC_VERSION_REQUIRED)
  if (NOT ISPC_EXECUTABLE)
  # try sibling folder as hint for path of ISPC
  if (APPLE)
  - set(ISPC_DIR_SUFFIX "osx" "Darwin")
  + set(ISPC_DIR_SUFFIX "macOS" "osx" "Darwin")
  elseif(WIN32)
  set(ISPC_DIR_SUFFIX "windows" "win32")
  if (MSVC_VERSION LESS 1900)
  @@ -32,8 +32,8 @@ if (NOT ISPC_EXECUTABLE)
  else()
  set(ISPC_DIR_SUFFIX "linux" "Linux")
  endif()
  - foreach(v "" "v")
  foreach(ver ${ISPC_VERSION_WORKING})
  + foreach(v "" "v")
  foreach(suffix ${ISPC_DIR_SUFFIX})
  foreach(d "" "/bin")
  list(APPEND ISPC_DIR_HINT ${PROJECT_SOURCE_DIR}/../ispc-${v}${ver}-${suffix}${d})
  