In some environments (gcc treated as error in W=1, which is default), if we
make -C samples/bpf/, it will be stopped because of
"no previous prototype" error like this:
../samples/bpf/syscall_nrs.c:7:6:
error: no previous prototype for ‘syscall_defines’ [-Werror=missing-prototypes]
void syscall_defines(void)
^~~~~~~~~~~~~~~
Actually, this file meets our expectatations because it will be converted to
a .h file. In this way, it's correct. Considering the warnning stopping us
compiling, we can remove the warnning directly.