graph-depends: fix when $(O) is a relative path

The graph-depends commands cd into the CONFIG_DIR and run the script
from there. However, this means that when $(O) is a relative path, it
will no longer be correct.  Therefore, use $(BASE_DIR) instead of $(O).

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Makefile

@@ -681,8 +681,8 @@ graph-depends: graph-depends-requirements
 	@$(INSTALL) -d $(O)/graphs
 	@cd "$(CONFIG_DIR)"; \
 	$(TOPDIR)/support/scripts/graph-depends $(BR2_GRAPH_DEPS_OPTS) \
-	|tee $(O)/graphs/$(@).dot \
-	|dot $(BR2_GRAPH_DOT_OPTS) -T$(BR_GRAPH_OUT) -o $(O)/graphs/$(@).$(BR_GRAPH_OUT)
+	|tee $(BASE_DIR)/graphs/$(@).dot \
+	|dot $(BR2_GRAPH_DOT_OPTS) -T$(BR_GRAPH_OUT) -o $(BASE_DIR)/graphs/$(@).$(BR_GRAPH_OUT)
 
 else # ifeq ($(BR2_HAVE_DOT_CONFIG),y)