Tighter pledge(2) for nm(1)/size(1)

[Theo Buehler]

nm(1) was tamed shortly before the "exec" promise was introduced.  The
"proc exec" is necessary to cover `nm -C' which fork-exec's c++filt(1).
Right after potential fork-exec, the original pledge "stdio rpath" is
given (one could make that last pledge call in the file conditional on
`issize' so that size only pledges once, but that complication doesn't
seem to be worth it).

Index: usr.bin/nm/nm.c
===================================================================
RCS file: /cvs/src/usr.bin/nm/nm.c,v
retrieving revision 1.49
diff -u -p -r1.49 nm.c
--- usr.bin/nm/nm.c     9 Oct 2015 01:37:08 -0000       1.49
+++ usr.bin/nm/nm.c     13 Nov 2015 13:38:20 -0000
@@ -135,10 +135,16 @@ main(int argc, char *argv[])
        const struct option *lopts;
        int ch, eval;
 
+       if (pledge("stdio rpath proc exec", NULL) == -1)
+               err(1, "pledge");
+
        optstr = OPTSTRING_NM;
        lopts = longopts_nm;
        if (!strcmp(__progname, "size")) {
-               issize++;
+               if (pledge("stdio rpath", NULL) == -1)
+                       err(1, "pledge");
+
+               issize = 1;
                optstr = "tw";
                lopts = NULL;
        }