The functions in locarchive.c cannot create files in non-default
locations.  Rather than enhancing locarchive.c (and risk regressions
in localedef), this patch adapts build-locale-archive to use the
existing output_prefix configuration variable.

Index: glibc-2.17-c758a686/releng/build-locale-archive.c
===================================================================
--- glibc-2.17-c758a686.orig/releng/build-locale-archive.c
+++ glibc-2.17-c758a686/releng/build-locale-archive.c
@@ -92,23 +92,34 @@ xmalloc (size_t size)
   return p;
 }
 
+static char *
+xasprintf (const char *format, ...)
+{
+  va_list ap;
+  va_start (ap, format);
+  char *result;
+  if (vasprintf (&result, format, ap) < 0)
+    error (EXIT_FAILURE, errno, "could not format string");
+  va_end (ap);
+  return result;
+}
+
 static void
 open_tmpl_archive (struct locarhandle *ah)
 {
   struct stat64 st;
   int fd;
   struct locarhead head;
-  const char *archivefname = ah->fname == NULL ? tmpl_file : ah->fname;
 
   /* Open the archive.  We must have exclusive write access.  */
-  fd = open64 (archivefname, O_RDONLY);
+  fd = open64 (tmpl_file, O_RDONLY);
   if (fd == -1)
     error (EXIT_FAILURE, errno, "cannot open locale archive template file \"%s\"",
-	   archivefname);
+	   tmpl_file);
 
   if (fstat64 (fd, &st) < 0)
     error (EXIT_FAILURE, errno, "cannot stat locale archive template file \"%s\"",
-	   archivefname);
+	   tmpl_file);
 
   /* Read the header.  */
   if (TEMP_FAILURE_RETRY (read (fd, &head, sizeof (head))) != sizeof (head))
@@ -253,12 +264,11 @@ compute_data (struct locarhandle *ah, st
 
 static int
 fill_archive (struct locarhandle *tmpl_ah,
-	      const char *fname,
 	      size_t install_langs_count, char *install_langs_list[],
 	      size_t nlist, char *list[],
 	      const char *primary)
 {
-  struct locarhandle ah;
+  struct locarhandle ah = {};
   struct locarhead *head;
   int result = 0;
   struct nameent *names;
@@ -338,9 +348,6 @@ fill_archive (struct locarhandle *tmpl_a
 
   /* Open the archive.  This call never returns if we cannot
      successfully open the archive.  */
-  ah.fname = NULL;
-  if (fname != NULL)
-    ah.fname = fname;
   open_archive (&ah, false);
 
   if (primary != NULL)
@@ -619,38 +626,39 @@ Usage: build-locale-archive [OPTION]...
                              \"de\" but also the aliases \"deutsch\"\n\
                              and and \"german\" although the latter does not\n\
                              start with \"de\".\n\
+  --prefix=DIR               Operate under the file system root DIR\n\
 \n\
-  If the arguments TEMPLATE-FILE and ARCHIVE-FILE are not given the locations\n\
-  where the glibc used expects these files are used by default.\n\
 ");
 }
 
 int main (int argc, char *argv[])
 {
-  char path[4096];
   DIR *dirp;
   struct dirent64 *d;
   struct stat64 st;
   char *list[16384], *primary;
   char *lang;
   int install_langs_count = 0;
-  int i;
   char *install_langs_arg, *ila_start;
   char **install_langs_list;
   unsigned int cnt = 0;
-  struct locarhandle tmpl_ah;
-  char *new_locar_fname = NULL;
-  size_t loc_path_len = strlen (loc_path);
+  struct locarhandle tmpl_ah = {};
 
   while (1)
     {
       int c;
 
+      enum
+      {
+	opt_prefix = 1000,
+      };
+
       static struct option long_options[] =
         {
             {"help",            no_argument,       0, 'h'},
             {"verbose",         no_argument,       0, 'v'},
             {"install-langs",   required_argument, 0, 'l'},
+	    {"prefix",          required_argument, 0, opt_prefix},
             {0, 0, 0, 0}
         };
       /* getopt_long stores the option index here. */
@@ -721,6 +729,10 @@ int main (int argc, char *argv[])
             }
           break;
 
+	case opt_prefix:
+	  output_prefix = optarg;
+	  break;
+
         case '?':
           /* getopt_long already printed an error message. */
           usage ();
@@ -730,23 +742,26 @@ int main (int argc, char *argv[])
           abort ();
         }
     }
-  tmpl_ah.fname = NULL;
-  if (optind < argc)
-    tmpl_ah.fname = argv[optind];
-  if (optind + 1 < argc)
-    new_locar_fname = argv[optind + 1];
+  if (optind != argc)
+    {
+      usage ();
+      exit (1);
+    }
+  if (output_prefix)
+    {
+      tmpl_file = xasprintf ("%s%s", output_prefix, tmpl_file);
+      alias_file = xasprintf ("%s%s", output_prefix, alias_file);
+      locar_file = xasprintf ("%s%s", output_prefix, locar_file);
+      loc_path = xasprintf ("%s%s", output_prefix, loc_path);
+    }
   if (verbose)
     {
-      if (tmpl_ah.fname)
-        printf("input archive file specified on command line: %s\n",
-               tmpl_ah.fname);
-      else
-        printf("using default input archive file.\n");
-      if (new_locar_fname)
-        printf("output archive file specified on command line: %s\n",
-               new_locar_fname);
-      else
-        printf("using default output archive file.\n");
+      if (output_prefix != NULL)
+	printf ("output prefix: %s\n", output_prefix);
+      printf ("input archive file: %s\n", tmpl_file);
+      printf ("input alias file: %s\n", alias_file);
+      printf ("input locale directory prefix: %s\n", loc_path);
+      printf ("output archive file: %s\n", locar_file);
     }
 
   dirp = opendir (loc_path);
@@ -754,11 +769,7 @@ int main (int argc, char *argv[])
     error (EXIT_FAILURE, errno, "cannot open directory \"%s\"", loc_path);
 
   open_tmpl_archive (&tmpl_ah);
-
-  if (new_locar_fname)
-    unlink (new_locar_fname);
-  else
-    unlink (locar_file);
+  unlink (locar_file);
 
   primary = getenv ("LC_ALL");
   if (primary == NULL)
@@ -790,8 +801,6 @@ int main (int argc, char *argv[])
 	}
     }
 
-  memcpy (path, loc_path, loc_path_len);
-
   while ((d = readdir64 (dirp)) != NULL)
     {
       if (strcmp (d->d_name, ".") == 0 || strcmp (d->d_name, "..") == 0)
@@ -799,32 +808,25 @@ int main (int argc, char *argv[])
       if (strchr (d->d_name, '_') == NULL)
 	continue;
 
-      size_t d_name_len = strlen (d->d_name);
-      if (loc_path_len + d_name_len + 1 > sizeof (path))
-	{
-	  error (0, 0, "too long filename \"%s\"", d->d_name);
-	  continue;
-	}
-
-      memcpy (path + loc_path_len, d->d_name, d_name_len + 1);
+      char *path = xasprintf ("%s%s", loc_path, d->d_name);
       if (stat64 (path, &st) < 0)
 	{
 	  error (0, errno, "cannot stat \"%s\"", path);
+	  free (path);
 	  continue;
 	}
       if (! S_ISDIR (st.st_mode))
-	continue;
+	{
+	  free (path);
+	  continue;
+	}
       if (cnt == 16384)
 	{
 	  error (0, 0, "too many directories in \"%s\"", loc_path);
+	  free (path);
 	  break;
 	}
-      list[cnt] = strdup (path);
-      if (list[cnt] == NULL)
-	{
-	  error (0, errno, "cannot add file to list \"%s\"", path);
-	  continue;
-	}
+      list[cnt] = path;
       if (primary != NULL && cnt > 0 && strcmp (primary, d->d_name) == 0)
 	{
 	  char *p = list[0];
@@ -836,7 +838,7 @@ int main (int argc, char *argv[])
   closedir (dirp);
   /* Store the archive to the file specified as the second argument on the
      command line or the default locale archive.  */
-  fill_archive (&tmpl_ah, new_locar_fname,
+  fill_archive (&tmpl_ah,
                 install_langs_count, install_langs_list,
                 cnt, list, primary);
   close_archive (&tmpl_ah);