Move cache outside of build-dYYMMDD directory so it can be cached

Travis allows us to cache directories between builds. Let make it
easier.

.travis.yml

@@ -1,6 +1,10 @@
 dist: bionic
 
 language: bash # same as minimal
+cache:
+  directories:
+    - $HOME/build/$TRAVIS_REPO_SLUG/../ccache
+    - $HOME/build/$TRAVIS_REPO_SLUG/../download
 
 install: 
   - bin/system-setup

Makefile

@@ -14,7 +14,7 @@ DISK_IMG = $(OUT_D)/disk.img
 PART_IMG = $(OUT_D)/part.img
 TAR_IMG = $(OUT_D)/rootfs.tar
 BR_TAR_IMG = $(BR_OUT_D)/images/rootfs.tar
-BR2_CCACHE_DIR = $(OUT_D)/ccache
+BR2_CCACHE_DIR = $(TOP_D)/ccache/$(ARCH)
 
 BR_MAKE = cd $(BR_D) && mkdir -p "$(TMPDIR)" && \
    make O=$(BR_OUT_D) BR2_DL_DIR=$(DL_D) \

bin/build-release

@@ -188,6 +188,8 @@ logevent "end kernel and grub downloads" "$kstart"
 # STAGE 2: BUILD
 jobs_flag=""
 parallel=true
+mkdir -p ../ccache
+ln -snf ../ccache ccache
 case "${CIRROS_PARALLEL:-none}" in
     none) parallel=false;;
     0|true) :;;