Avoid race condition with concurrent directory creation.
--- xinstall.c.orig
+++ xinstall.c
@@ -831,8 +831,13 @@ install_dir(char *path)
 			*p = '\0';
 			if (stat(path, &sb)) {
 				if (errno != ENOENT || mkdir(path, 0755) < 0) {
-					err(EX_OSERR, "mkdir %s", path);
-					/* NOTREACHED */
+					/* Check if the dir was created between
+					 * our stat and mkdir calls. */
+					int saved_errno = errno;
+					if (errno != EEXIST || stat(path, &sb) < 0 || !S_ISDIR(sb.st_mode)) {
+					    errc(EX_OSERR, saved_errno, "mkdir %s", path);
+					    /* NOTREACHED */
+					}
 				} else if (verbose)
 					(void)printf("install: mkdir %s\n",
 						     path);