Fixed GCC version bug in CIBB_64b script.

Author: abhiTronix

build-scripts/CI/CIBB_64b

@@ -71,11 +71,15 @@ else
 	exit
 fi
 
-# exit if GCC < 8.3.0 for buster
-if [ "$RPIOS_TYPE" = "buster" ] && [ "$GCC_VERSION" \< "8.3.0" ]; then
+# exit if not valid GCC
+if [ "$RPIOS_TYPE" = "buster" ] && [ "$GCC_VERSION" != "8.3.0" ]; then
 	echo "Invalid GCC for buster: $GCC_VERSION!"
 	exit
 fi
+if [ "$RPIOS_TYPE" = "stretch" ] && [ "$GCC_VERSION" != "6.3.0" ]; then
+	echo "Invalid GCC for stretch: $GCC_VERSION!"
+	exit
+fi
 
 #collect build directory if not defined
 if [ "$BUILDDIR" = "" ]; then