Use eclass functions to install under PEP517

Patch to ensure failure if the change fails to apply.

--- a/sepolicy/Makefile
+++ b/sepolicy/Makefile
@@ -27,7 +27,6 @@ test:
 	@$(PYTHON) test_sepolicy.py -v
 
 install:
-	$(PYTHON) -m pip install --prefix=$(PREFIX) `test -n "$(DESTDIR)" && echo --root $(DESTDIR) --ignore-installed --no-deps` $(PYTHON_SETUP_ARGS) .
 	[ -d $(DESTDIR)$(BINDIR) ] || mkdir -p $(DESTDIR)$(BINDIR)
 	install -m 755 sepolicy.py $(DESTDIR)$(BINDIR)/sepolicy
 	(cd $(DESTDIR)$(BINDIR); ln -sf sepolicy sepolgen)