a68: avoid conditional expression in sppp.awk

The macOS awk seems to not like having an unparenthesized conditional
expression as the last argument to printf.  This commit workarounds
this by simply replacing the conditional expression with a conditional
statement.

Tested with gawk and mawk.

Signed-off-by: Jose E. Marchesi <jemarch@gnu.org>

libga68/ChangeLog

	* sppp.awk: Avoid conditional expression.

libga68/sppp.awk

@@ -114,7 +114,11 @@ BEGIN {
         {
             while (sub ("\\{" iter_name "\\}", iterators[iter_name,nalt], output)) {}
         }
-        printf "%s%s\n", substr (output, 0, length(output) - 1), nalt < num_alternatives ? separator : ""
+        if (nalt < num_alternatives)
+            sep = separator
+        else
+            sep = ""
+        printf "%s%s\n", substr (output, 0, length(output) - 1), sep
     }
 
     for (key in iter_names) delete iter_names[key]