Fix a compilation error when GPROF is defined.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1857859 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/server/core.c b/server/core.c
index 2ce5af7..96709f2 100644
--- a/server/core.c
+++ b/server/core.c
@@ -1633,7 +1633,7 @@
         return err;
     }
 
-    conf->gprof_dir = arg;
+    conf->gprof_dir = apr_pstrdup(cmd->pool, arg);
     return NULL;
 }
 #endif /*GPROF*/