Add missing file to NATDEPFILES.
gdb/ChangeLog:
2017-11-24  Ulrich Weigand  <uweigand@de.ibm.com>
	* configure.nat <spu-linux>: Add fork-inferior.o to NATDEPFILES.
+2017-11-24  Ulrich Weigand  <uweigand@de.ibm.com>
+
+       * configure.nat <spu-linux>: Add fork-inferior.o to NATDEPFILES.
+
 2017-11-24  Philipp Rudo  <prudo@linux.vnet.ibm.com>
 
        * dtrace-probe.c (dtrace_probe::build_arg_exprs)
 
                NAT_FILE=
                NAT_CDEPS=
                LOADLIBES=
-               NATDEPFILES='spu-linux-nat.o fork-child.o inf-ptrace.o \
+               NATDEPFILES='spu-linux-nat.o \
+                     inf-ptrace.o fork-child.o fork-inferior.o \
                      linux-procfs.o linux-ptrace.o linux-waitpid.o \
                      linux-personality.o linux-namespaces.o'
                ;;