[source] Makefile: ensure that BIN_DIR exists for diffconfig

[LEDE Commits]

nbd pushed a commit to source.git, branch master:
https://git.lede-project.org/c1b12aa838587952b269a75ad278e8805aa9a65f

commit c1b12aa838587952b269a75ad278e8805aa9a65f
Author: Hannu Nyman <hannu.nyman at iki.fi>
AuthorDate: Fri Jan 6 19:51:35 2017 +0200

    Makefile: ensure that BIN_DIR exists for diffconfig
    
    Ensure that BIN_DIR exists when the diffconfig target needs it.
    Otherwise 'make diffconfig' fails after 'make clean'
    
    Signed-off-by: Hannu Nyman <hannu.nyman at iki.fi>
---
 Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Makefile b/Makefile
index 3450f7e..b220dfd 100644
--- a/Makefile
+++ b/Makefile
@@ -88,6 +88,7 @@ checksum: FORCE
 	$(call sha256sums,$(BIN_DIR))
 
 diffconfig: FORCE
+	mkdir -p $(BIN_DIR)
 	$(SCRIPT_DIR)/diffconfig.sh > $(BIN_DIR)/config.seed
 
 prepare: .config $(tools/stamp-install) $(toolchain/stamp-install)