config: Only build as dynamic module when really requested

Since commit 37182ce the module was always build as dynamic module.
Probably because following a bad skeleton [1].

With this change we will only build a dynamic module when requested. Otherwise
we will fall back to static build.

Link: https://trac.nginx.org/nginx/ticket/1115
Gentoo-Bug: https://bugs.gentoo.org/593450
Fixes: #50

Author: Whissi

config

@@ -1,5 +1,5 @@
 ngx_addon_name=ngx_http_uploadprogress_module
-if test -n "$ngx_module_link"; then
+if [ $ngx_module_link = DYNAMIC ] ; then
     ngx_module_type=FILTER
     ngx_module_name=ngx_http_uploadprogress_module
     ngx_module_srcs="$ngx_addon_dir/ngx_http_uploadprogress_module.c"