bindings: python: fix package installation with Makefile build

The modules are installed in the .egg directory, and therefore cannot be
imported after that. Specify correct --root and fix the --prefix switch.

Link: pypa/pip#3063
Suggested-by: Maxim Devaev <[email protected]>
Reported-by: Maxim Devaev <[email protected]>
Signed-off-by: Bartosz Golaszewski <[email protected]>

Author: Bartosz Golaszewski

bindings/python/Makefile.am

@@ -19,7 +19,7 @@ all-local:
 
 install-exec-local:
 	GPIOD_WITH_TESTS= \
-	$(PYTHON) setup.py install --prefix=$(DESTDIR)$(prefix)
+	$(PYTHON) setup.py install --root=$(if $(DESTDIR),$(DESTDIR),/) --prefix=$(prefix)
 
 SUBDIRS = gpiod