Use eclass functions to install under PEP517

Patch to ensure failure if the change fails to apply.
--- a/sepolicy/Makefile
+++ b/sepolicy/Makefile
@@ -26,7 +26,6 @@ test:
 	@$(PYTHON) test_sepolicy.py -v
 
 install: python-build
-	$(PYTHON) -m pip install --no-build-isolation --force-reinstall --prefix=$(PREFIX) `test -n "$(DESTDIR)" && echo --root $(DESTDIR) --ignore-installed --no-deps` dist/*.whl
 	[ -d $(DESTDIR)$(BINDIR) ] || mkdir -p $(DESTDIR)$(BINDIR)
 	install -m 755 sepolicy.py $(DESTDIR)$(BINDIR)/sepolicy
 	(cd $(DESTDIR)$(BINDIR); ln -sf sepolicy sepolgen)