useradd: use "cp" instead of "pax" to copy dot files

[Todd C . Miller]

We can just use "cp -a skeldir/. homedir" to copy the skeleton dot
files to the new user's homedir.  There's no good reason to use pax
when cp will do and this will simplify a future commit of mine.

 - todd

Index: usr.sbin/user/user.c
===================================================================
RCS file: /cvs/src/usr.sbin/user/user.c,v
retrieving revision 1.129
diff -u -p -u -r1.129 user.c
--- usr.sbin/user/user.c        15 May 2023 17:00:24 -0000      1.129
+++ usr.sbin/user/user.c        16 May 2023 17:30:18 -0000
@@ -171,7 +171,7 @@ enum {
 #define MKDIR          "/bin/mkdir"
 #define MV             "/bin/mv"
 #define NOLOGIN                "/sbin/nologin"
-#define PAX            "/bin/pax"
+#define CP             "/bin/cp"
 #define RM             "/bin/rm"
 
 #define UNSET_INACTIVE "Null (unset)"
@@ -311,8 +311,8 @@ copydotfiles(char *skeldir, char *dir)
        if (n == 0) {
                warnx("No \"dot\" initialisation files found");
        } else {
-               (void) asystem("cd %s && %s -rw -pe %s . %s",
-                               skeldir, PAX, (verbose) ? "-v" : "", dir);
+               (void) asystem("%s -a %s %s/. %s",
+                   CP, (verbose) ? "-v" : "", skeldir, dir);
        }
        return n;
 }