feat: install most dependencies in cacheable layer, before adding main

Instead of requiring the whole stack to be reinstalled whenever a specific version (e.g. main) causes a cache fail, this aims to have stable default version with a second-stage installation of the potentially-modified versions of eicrecon and juggler. This should allow all builds to cache the first installation in virtually all cases, leading to faster builds.

containers/jug/dev.Dockerfile

@@ -70,14 +70,6 @@ spack compiler find --scope site
 spack config blame compilers
 EOF
 
-## Setup local buildcache mirrors
-RUN --mount=type=cache,target=/var/cache/spack <<EOF
-set -e
-spack mirror add local /var/cache/spack/mirror/${SPACK_VERSION}
-spack buildcache update-index local
-spack mirror list
-EOF
-
 ## Setup eics3 buildcache mirrors
 ## - this always adds the read-only mirror to the container
 ## - the write-enabled mirror is provided later as a secret mount
@@ -140,7 +132,7 @@ RUN --mount=type=cache,target=/ccache,id=${TARGETPLATFORM}              \
     <<EOF
 set -e
 export CCACHE_DIR=/ccache
-spack buildcache update-index local
+find /var/cache/spack/blobs/sha256/ -atime +7 -delete
 spack buildcache update-index eics3rw
 spack env activate --dir ${SPACK_ENV}
 spack concretize --fresh --force --quiet
@@ -170,7 +162,7 @@ if [ -n ${EICRECON_VERSION} ] ; then
   spack config add "packages:eicrecon::require:['@git.${EICRECON_VERSION}']"
 fi
 spack concretize --fresh --force --quiet
-make --jobs ${jobs} --keep-going --directory /opt/spack-environment SPACK_ENV=${SPACK_ENV} BUILDCACHE_MIRROR="local eics3rw"
+make --jobs ${jobs} --keep-going --directory /opt/spack-environment SPACK_ENV=${SPACK_ENV} BUILDCACHE_MIRROR_ONLY_PACKAGE="eics3rw" BUILDCACHE_MIRROR_DEPENDENCIES="eicweb ghcr"
 ccache --show-stats
 ccache --zero-stats
 EOF
@@ -178,9 +170,8 @@ EOF
 ## Create view at /usr/local
 RUN --mount=type=cache,target=/var/cache/spack <<EOF
 set -e
-spack env activate --dir ${SPACK_ENV}
 rm -r /usr/local
-spack env view enable /usr/local
+spack -e ${SPACK_ENV} env view enable /usr/local
 EOF
 
 ## Optional, nuke the buildcache after install, before (re)caching