Add to Makefile.example note about +x

Since only try.sh and try.alt.sh files may be executable in submission
tarballs, the Makefile.example now notes this and shows how one can
adjust this if they need to. This is also in the guidelines, rules and
FAQ but those cannot be committed yet.

next/Makefile.example

@@ -153,12 +153,16 @@ ALT_TARGET=
 #
 DATA=
 
-
 #################
 # build the entry
 #################
 
 all: data ${TARGET}
+	# NOTE: only try.sh and try.alt.sh scripts will be made executable in
+	# the tarball so if you need any scripts that are executable, make sure
+	# to use ${CHMOD} +x on them like:
+	#
+	#   ${CHMOD} +x foo.sh
 
 .PHONY: all data try clean clobber install