#3704 file extension output by -M option is wrong

[kwhr00]

example:
a.h

#define A 0

a.c

#include "a.h"
int main() {
    return A;
}

command line

$ sdcc -mz80 -MM a.c

output of SDCC 4.1.0 ; correct

a.rel: a.c a.h

output of SDCC 4.4.0 RC3 ; wrong

a.o: a.c a.h