use explicit include for the proxy cache directive.

nginx.conf

@@ -42,6 +42,9 @@ http {
     keepalive_timeout  300;
     gzip  off;
 
+    # Entrypoint generates the proxy_cache_path here, so it is configurable externally.
+    include /etc/nginx/conf.d/cache_max_size.conf;
+
     # Just in case you want to rewrite some hosts. Default maps directly.
     map $host $targetHost {
         hostnames;
@@ -89,8 +92,6 @@ http {
         default "DID_NOT_MATCH_PATH";
     }
 
-    include /etc/nginx/conf.d/*.conf;
-
 
     # The proxy director layer, listens on 3128
     server {