This adds pypi.mk, which can be included in Python packages that
download their sources from PyPI, to auto-fill various PKG_* variables
based on the value of PYPI_NAME.
This makefile should be included after $(TOPDIR)/rules.mk but before
$(INCLUDE_DIR)/package.mk (and $(INCLUDE_DIR)/host-build.mk).
Signed-off-by: Jeffery To <jeffery.to@gmail.com>
