minor #6846 Adds bin folder creation instruction (joelrfcosta)

This PR was submitted for the 3.1 branch but it was merged into the 2.7 branch instead (closes #6846).

Discussion
----------

Adds bin folder creation instruction

On some cases, after OS installation, the user/local/bin folder does not exists. Adding this instruction will avoid curl issues.

Commits
-------

65a5025 Adds bin folder creation instruction

Author: weaverryan

setup.rst

@@ -17,6 +17,7 @@ executable that needs to be installed on your system only once:
 .. code-block:: bash
 
     # Linux and macOS systems
+    $ sudo mkdir -p /usr/local/bin
     $ sudo curl -LsS https://symfony.com/installer -o /usr/local/bin/symfony
     $ sudo chmod a+x /usr/local/bin/symfony