configure: Report why the *write_prometheus plugin* is disabled.

diff --git a/configure.ac b/configure.ac
index 01e8193036826c6d51497d017fca789c111b277a..01b5c2316dae03f3214edcd3bf56f8e174ce5801 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -7145,6 +7145,8 @@ fi
 
 if test "x$with_libmicrohttpd" = "xyes"; then
   plugin_write_prometheus="yes"
+else
+  plugin_write_prometheus="no (libmicrohttpd not found)"
 fi
 
 # Mac OS X memory interface