Improve how to redefine macro in 2004/jdalbec

Now one can do

    make clobber Ag=47 alt

to make the number of numbers on a single line 47 (of course at the same
time as defeating the purpose :-) ).

2004/jdalbec/Makefile

@@ -56,9 +56,12 @@ CSTD= -ansi
 #
 ARCH=
 
+# variable for redefining macro Ag
+#
+Ag= 11
 # Defines that are needed to compile
 #
-CDEFINE= -DAg=11
+CDEFINE= -DAg=${Ag}
 
 # Include files that are needed to compile
 #

2004/jdalbec/README.md

@@ -52,7 +52,7 @@ you wish to make it silver, 47 (a prime) protons, do:
 
 
 ```sh
-make clobber CDEFINE="-DAg=47" alt
+make clobber Ag=47 alt
 ```
 
 though it might be odd to have 47 numbers on a line as it would defeat the
@@ -60,7 +60,7 @@ purpose. :-) Or if you prefer some prime, golden irony:
 
 
 ```sh
-make clobber CDEFINE="-DAg=79" alt
+make clobber Ag=79 alt
 ```