[openwrt/openwrt] imagebuilder: clean KDIR_TMP before building

[LEDE Commits]

aparcar pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/fee31628c422e71c5ab0985ce10e960dad3c87f2

commit fee31628c422e71c5ab0985ce10e960dad3c87f2
Author: Paul Spooren <mail at aparcar.org>
AuthorDate: Sat Sep 10 16:35:31 2022 +0200

    imagebuilder: clean KDIR_TMP before building
    
    Building images usally stores them in KDIR_TMP and then copies them over
    to BIN_DIR. This is fine as rebuilding of images overwrites existing
    images. When using the EXTRA_IMAGE_NAME variable frequently this fills
    up the ImageBuilder KDIR_TMP folder since every built image is stored
    forever.
    
    This commit clears the KDIR_TMP folder before building a new image.
    
    Below an example how sysupgrade.openwrt.org filled up after the release
    of 22.03.0 where every created image contains a hash of the package
    selction in the filename:
    
         aparcar at asu-01:~/asu/worker1/cache/22.03.0$ du -d 1 -h
         400M    ./kirkwood
         260M    ./gemini
         2.0G    ./ipq806x
         1.7G    ./ipq40xx
         8.1G    ./ramips
         4.0K    ./octeon
         495M    ./sunxi
         728M    ./lantiq
         1.8G    ./rockchip
         3.7G    ./mediatek
         4.0K    ./realtek
         5.4G    ./mvebu
         8.9G    ./ath79
         3.0G    ./bcm47xx
         14G     ./bcm27xx
         11G     ./x86
         4.0K    ./bcm63xx
         312M    ./mpc85xx
         600M    ./apm821xx
         5.4G    ./bcm53xx
         66G     .
    
    Signed-off-by: Paul Spooren <mail at aparcar.org>
---
 include/image.mk | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/image.mk b/include/image.mk
index bdcf20d30c..9e4e999581 100644
--- a/include/image.mk
+++ b/include/image.mk
@@ -756,6 +756,7 @@ define BuildImage
 
   else
     image_prepare:
+		rm -rf $(KDIR)/tmp
 		mkdir -p $(BIN_DIR) $(KDIR)/tmp
   endif