pylibfdt/Makefile.pylibfdt: fix Python library being rebuild during install

The Python module gets built during the 'make install' command even if
'make all' was run prior for build.

This is the same issue as described in the previous commit
"pylibfdt/meson.build: fix Python library being rebuilt during install".
Remove the '--build-lib' flag so setuptools can find the build module.

Signed-off-by: Brandon Maier <brandon.maier@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

pylibfdt/Makefile.pylibfdt

@@ -17,7 +17,7 @@ endif
 
 $(PYMODULE): $(PYLIBFDT_srcs) $(LIBFDT_archive) $(SETUP)
 	@$(VECHO) PYMOD $@
-	$(PYTHON) $(SETUP) $(SETUPFLAGS) build_ext --build-lib=$(PYLIBFDT_dir)
+	$(PYTHON) $(SETUP) $(SETUPFLAGS) build_ext
 
 install_pylibfdt: $(PYMODULE)
 	@$(VECHO) INSTALL-PYLIB