No need to remake target `pi.c'.
   Finished prerequisites of target file `pi.o'.
  Must remake target `pi.o'.
gcc -c pi.c
Putting child 0x000558c8 (pi.o) PID 22129 on the chain.
Live child 0x000558c8 (pi.o) PID 22129
Reaping winning child 0x000558c8 PID 22129
Removing child 0x000558c8 PID 22129 from chain.
  Successfully remade target file `pi.o'.
 Finished prerequisites of target file `hello'.
Must remake target `hello'.
gcc -lm -o hello hello.o pi.o
Putting child 0x000558f0 (hello) PID 22132 on the chain.
Live child 0x000558f0 (hello) PID 22132
Reaping winning child 0x000558f0 PID 22132
Removing child 0x000558f0 PID 22132 from chain.
Successfully remade target file `hello'.