Cleanup tox command handling.

Long winding road for this patch:
  Interest: Support local python and tox upgrades to facilitate working
            on robot testing framework used by broadband.
            Support a common python and tox versions across repos.
     Wonky: tox was used indirectly as a lint dependency (lint-jjb).
            The lint target is only used by repo:ci-management for JJB.
            Modify to make it a standalone usable comand/dependency.

makefiles/target/tox.mk
-----------------------
  o File deprecation pending, only used by repo:ci-management.

makefiles/include.mk
makefiles/commands/include.mk
makefiles/lint/include.mk
-----------------------------
  o Restructure: include logic, installer and version from commands/tox/.

makefiles/commands/tox/README.md
makefiles/commands/include.mk
makefiles/commands/tox/include.mk
makefiles/commands/tox/install.mk
makefiles/commands/tox/requirements.txt
makefiles/commands/tox/tox.mk
---------------------------------------
  o Added targets:
    + tox-version: Display version of venv installed tox command.
    + tox-install: Install a versioned tox command (requirements.txt).
    + help: display basic target help.
    + tox-help: display extended help for tox-*.
  o Added 3.11.6 to the supported list of python interpreters for local use.

[HOWTO: Test]
  % make help | grep tox
  % make tox-help

  # Install venv + tox
  % make sterile tox-version
  % make sterile tox
  % make sterile tox-install

Change-Id: I8a7c1fe84727b8ec282c4c03e953b8052d2bf242
diff --git a/makefiles/virtualenv/requirements-txt.mk b/makefiles/virtualenv/requirements-txt.mk
index c524449..2d615f6 100644
--- a/makefiles/virtualenv/requirements-txt.mk
+++ b/makefiles/virtualenv/requirements-txt.mk
@@ -43,9 +43,8 @@
 $(venv-requirements) : requirements.txt
 
 	$(call banner-enter,venv-requirements)
-
-	$(activate) && python -m pip install -r 'requirements.txt'
 	@mkdir -p $(dir $@)
+	$(activate) && python -m pip install -r 'requirements.txt'
 	@touch $@
 
 	$(call banner-leave,venv-requirements)