Atreus: Add build date/time to version info

Example output:

    Keyboardio Atreus - Kaleidoscope locally built on Sep  3 2021 at 09:40:27

Signed-off-by: Florian Bruhin <me@the-compiler.org>

examples/Devices/Keyboardio/Atreus/Atreus.ino

@@ -18,7 +18,7 @@
  */
 
 #ifndef BUILD_INFORMATION
-#define BUILD_INFORMATION "locally built"
+#define BUILD_INFORMATION "locally built on " __DATE__ " at " __TIME__
 #endif
 
 #include "Kaleidoscope.h"