I made it in 0 (zero) characters:
cat src.c
(empty)
the resulting executable:
rbo@deneb ~
$ ./src
SUCCESS
and the command line:
rbo@deneb ~
$ echo x>>src.c && gcc -Dx="int main(){return puts(\"SUCCESS\");}" -o src src.c
But this of course still creates a source file with on character, as Pedro has pointed out below. Without any source file, the command would be (in a Unix environment):
rbo@deneb ~
echo 'int main(){return puts("SUCCESS");}'|gcc -ansi -o src -xc -
which is even shorter than the above. In the original description, there's no restriction stated how to solve it, but the OP adds in a later comment he can't change the command line. If this is true, then this is not really a Code Golf ;-)
Regards
rbo