Add PIP_REQUIRE_VENV handling as well.

Author: freakboy3742

Mac/BuildScript/resources/install_certificates.command

@@ -1,6 +1,7 @@
 #!/bin/sh
 # Installing into the global environment is the point; ensure that the user
 # hasn't configured pip to always require a virtual environment.
+unset PIP_REQUIRE_VENV
 unset PIP_REQUIRE_VIRTUALENV
 
 /Library/Frameworks/Python.framework/Versions/@PYVER@/bin/python@PYVER@ << "EOF"