Reduce pledge(2) on file(1)'s main proc

[Ricardo Mestre]

Hi,

After fork(2) the main proc needs rpath for {l,}stat/open and sendfd for imsg_*
to send fds to the child proc which is already pledged by recvfd to receive
them.

Still passes regress tests, OK?

Index: file.c
===================================================================
RCS file: /cvs/src/usr.bin/file/file.c,v
retrieving revision 1.68
diff -u -p -u -r1.68 file.c
--- file.c      5 Feb 2019 02:17:32 -0000       1.68
+++ file.c      29 Nov 2019 11:03:47 -0000
@@ -207,6 +207,9 @@ main(int argc, char **argv)
        }
        close(pair[1]);
 
+       if (pledge("stdio rpath sendfd", NULL) == -1)
+               err(1, "pledge");
+
        fclose(magicfp);
        magicfp = NULL;