Document the new FORTIFY and SANITIZE options

src/build/Common.gmake

@@ -53,8 +53,12 @@
 #					  (GCC/DEBUG only)										#
 #  GCOV				- Generates binaries that produce gcov data				#
 #					  (GCC/DEBUG only)										#
+#  FORTIFY          - Generates binaries that use _FORTIFY_SOURCE option    #
+#                     (DEBUG only)                                          #
+#  SANITIZE         - Enable the AddressSanitizer (ASan) and UB Sanitizer   #
+#                     (DEBUG only)                                          #
 #  RELEASE			- Create a release build								#
-#					  (Mutually exclusive, if both are set, RELEASE 		#
+#					  (Mutually exclusive, if DEBUG is set, RELEASE 		#
 #						is cleared)											#
 #  USE_UPROFILE		- Builds using information generated by UPROFILE.		#
 #					  (RELEASE builds only)									#