add extra check for compiler time (#499)

minor change to add extra check for compiler time to prevent bad config

Co-authored-by: Gaurav-Aggarwal-AWS <33462878+aggarg@users.noreply.github.com>
diff --git a/portable/ThirdParty/GCC/ATmega/port.c b/portable/ThirdParty/GCC/ATmega/port.c
index 8277949..f998cdb 100644
--- a/portable/ThirdParty/GCC/ATmega/port.c
+++ b/portable/ThirdParty/GCC/ATmega/port.c
@@ -61,6 +61,8 @@
     #define portTIMSK                   TIMSK0
     #define portTIFR                    TIFR0
 
+#else
+    #error "No Timer defined for scheduler"
 #endif
 
 /*-----------------------------------------------------------*/