rm: use gnulib faccessat

* bootstrap.conf (gnulib_modules): Add faccessat.  Replace strdup
with strdup-posix.
* m4/jm-macros.m4 (coreutils_MACROS): Revert previous change, now
that gnulib does it for us.
* src/remove.c (write_protected_non_symlink): Use faccessat in
more situations.

bootstrap.conf

@@ -78,6 +78,7 @@ gnulib_modules="
   euidaccess
   exclude
   exitfail
+  faccessat
   fchdir
   fcntl
   fcntl-safer
@@ -197,7 +198,7 @@ gnulib_modules="
   stdlib-safer
   stpcpy
   stpncpy
-  strdup
+  strdup-posix
   strftime
   strpbrk
   strtoimax

m4/jm-macros.m4

@@ -92,9 +92,6 @@ AC_DEFUN([coreutils_MACROS],
   # for cp.c
   AC_CHECK_FUNCS_ONCE([utimensat])
 
-  # for remove.c
-  AC_CHECK_FUNCS_ONCE([faccessat])
-
   dnl This can't use AC_REQUIRE; I'm not quite sure why.
   cu_PREREQ_STAT_PROG
 

src/remove.c

@@ -172,12 +172,11 @@ write_protected_non_symlink (int fd_cwd,
         mess up with long file names). */
 
   {
-    /* Use faccessat if possible, so as to avoid the expense
-       of processing an N-component name.  */
-#if HAVE_FACCESSAT && AT_EACCESS
-    if (faccessat (fd_cwd, file, W_OK, AT_EACCESS) == 0)
+    /* This implements #1: on decent systems, either faccessat is
+       native or /proc/self/fd allows us to skip a chdir.  */
+    if (!openat_needs_fchdir ()
+        && faccessat (fd_cwd, file, W_OK, AT_EACCESS) == 0)
       return 0;
-#endif
 
     /* This implements #5: */
     size_t file_name_len = strlen (full_name);