Without this, when building with recent gcc, we'll see errors when
compiling for --target mmix the first being:
CC libc/sys/mmixware/libc_a-chmod.o
In file included from /x/newlib/libc/sys/mmixware/chmod.c:17:
/x/newlib/libc/sys/mmixware/chmod.c: In function 'chmod':
/x/newlib/libc/sys/mmixware/sys/syscall.h:139:6: error: implicit declaration \
of function 'sprintf' [-Wimplicit-function-declaration]
139 | sprintf (buf, "UNIMPLEMENTED %s in %s\n", __FUNCTION__,
__FILE__); \
Other warnings also quelled.
* libc/sys/mmixware/sys/syscall.h: Include stdio.h, string.h
and unistd.h.
* libc/sys/mmixware/_exit.c: Call __unreachable after simulator exit.
* libc/sys/mmixware/chown.c (chown): Match declaration in unistd.h.
* libc/sys/mmixware/getpid.c (_getpid): Ditto.
* libc/sys/mmixware/kill.c (_kill): Ditto.
* libc/sys/mmixware/link.c (_link): Ditto.
* libc/sys/mmixware/read.c (_read): Ditto.
* libc/sys/mmixware/sbrk.c (_sbrk): Ditto.
* libc/sys/mmixware/unlink.c (_unlink): Ditto.
* libc/sys/mmixware/write.c (_write): Ditto.
ddb614993a