ci: Cache stuff in volumes, not host folders

ci/test/00_setup_env.sh

@@ -8,11 +8,10 @@ export LC_ALL=C.UTF-8
 
 # The root dir.
 # The ci system copies this folder.
-# This is where the depends build is done.
 BASE_ROOT_DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )"/../../ >/dev/null 2>&1 && pwd )
 export BASE_ROOT_DIR
 # The depends dir.
-# This folder exists on the ci host and ci guest. Changes are propagated back and forth.
+# This folder exists only on the ci guest, and on the ci host as a volume.
 export DEPENDS_DIR=${DEPENDS_DIR:-$BASE_ROOT_DIR/depends}
 # A folder for the ci system to put temporary files (ccache, datadirs for tests, ...)
 # This folder only exists on the ci host.
@@ -58,12 +57,14 @@ export CCACHE_SIZE=${CCACHE_SIZE:-100M}
 export CCACHE_TEMPDIR=${CCACHE_TEMPDIR:-/tmp/.ccache-temp}
 export CCACHE_COMPRESS=${CCACHE_COMPRESS:-1}
 # The cache dir.
-# This folder exists on the ci host and ci guest. Changes are propagated back and forth.
+# This folder exists only on the ci guest, and on the ci host as a volume.
 export CCACHE_DIR=${CCACHE_DIR:-$BASE_SCRATCH_DIR/.ccache}
 # Folder where the build result is put (bin and lib).
 export BASE_OUTDIR=${BASE_OUTDIR:-$BASE_SCRATCH_DIR/out/$HOST}
 # Folder where the build is done (dist and out-of-tree build).
 export BASE_BUILD_DIR=${BASE_BUILD_DIR:-$BASE_SCRATCH_DIR/build}
+# The folder for previous release binaries.
+# This folder exists only on the ci guest, and on the ci host as a volume.
 export PREVIOUS_RELEASES_DIR=${PREVIOUS_RELEASES_DIR:-$BASE_ROOT_DIR/releases/$HOST}
 export SDK_URL=${SDK_URL:-https://bitcoincore.org/depends-sources/sdks}
 export CI_BASE_PACKAGES=${CI_BASE_PACKAGES:-build-essential libtool autotools-dev automake pkg-config bsdmainutils curl ca-certificates ccache python3 rsync git procps bison}