CI: Update the CI image to 4 and attach the serene volume

.woodpecker.yml

@@ -1,9 +1,9 @@
 pipeline:
   Prepare:
-    image: beta.devheroes.codes/serene/ci:3
+    image: beta.devheroes.codes/serene/ci:4
     commands:
-      - ls
-      - pwd
       - ./builder setup
       - ./builder deps pull toolchain
       - ./builder deps pull bdwgc
+    volumes:
+      - serene_config:/root/.serene

builder

@@ -61,12 +61,6 @@ LSAN_OPTIONS=suppressions=$(pwd)/.ignore_sanitize
 export LSAN_OPTIONS
 export LDFLAGS="-fuse-ld=lld"
 
-# The `builder` script is supposed to be run from the
-# root of the source tree
-ROOT_DIR=$(pwd)
-BUILD_DIR=$ROOT_DIR/build
-
-
 CMAKEARGS_DEBUG=("-DCMAKE_BUILD_TYPE=Debug")
 CMAKEARGS=("-DCMAKE_EXPORT_COMPILE_COMMANDS=ON"
            "-DSERENE_CCACHE_DIR=$HOME/.ccache")