Toybox grep on a directory hits a uClibc bug and segfaults. This bug does not
happen in glibc, musl, or bionic, so it's not worth adding a workaround
upstream.

diff -r dbee4e656aa6 toys/posix/grep.c
--- a/toys/posix/grep.c	Thu Mar 26 13:25:20 2015 -0500
+++ b/toys/posix/grep.c	Fri Mar 27 20:10:08 2015 -0500
@@ -62,16 +62,21 @@
 
 static void do_grep(int fd, char *name)
 {
-  FILE *file = fdopen(fd, "r");
+  struct stat *st = (void *)(toybuf+sizeof(regex_t));
+  FILE *file = 0;
   long offset = 0;
   int lcount = 0, mcount = 0, which = toys.optflags & FLAG_w ? 2 : 0;
   char indelim = '\n' * !(toys.optflags&FLAG_z),
        outdelim = '\n' * !(toys.optflags&FLAG_Z);
 
   if (!fd) name = "(standard input)";
-
+  if (!fstat(fd, st)) {
+    // grep * hits directories, skip but don't treat them as errors.
+    if (S_ISDIR(st->st_mode)) errno = 0;
+    else file = fdopen(fd, "r");
+  }
   if (!file) {
-    perror_msg("%s", name);
+    if (errno) perror_msg("%s", name);
     return;
   }
 
@@ -88,8 +93,7 @@
 
     start = line;
 
-    for (;;)
-    {
+    for (;;) {
       int rc = 0, skip = 0;
 
       if (toys.optflags & FLAG_F) {