Create .htaccess

Ref https://github.com/owncloud/core/pull/16724#discussion_r33236344 – shouldn't hurt also.

build/.htaccess

@@ -0,0 +1,12 @@
+# line below if for Apache 2.4
+<ifModule mod_authz_core.c>
+Require all denied
+</ifModule>
+
+# line below if for Apache 2.2
+<ifModule !mod_authz_core.c>
+deny from all
+</ifModule>
+
+# section for Apache 2.2 and 2.4
+IndexIgnore *