refactor: precompute package list in install-deps step to reduce matrix job memory usage

Move packages-to-build.R execution to the single install-deps step and save results as RDS. Matrix jobs read the precomputed list instead of loading the massive CRAN archive/release databases, freeing memory for fork/system calls.

.crow/build-all-versions-install-deps.yaml

@@ -17,6 +17,12 @@ steps:
         from_secret: REPO_RO_TOKEN
       GITHUB_PAT:
         from_secret: GITHUB_PAT
+      B2_S3_ACCESS_KEY:
+        from_secret: B2_S3_ACCESS_KEY
+      B2_S3_SECRET_KEY:
+        from_secret: B2_S3_SECRET_KEY
+      PGPASS:
+        from_secret: PGPASS
       R_PKG_CACHE_DIR: /mnt/cache/pkgcache
       R_LIBS_USER: /mnt/cache/R-pkgs
       CCACHE_DIR: /mnt/cache/ccache
@@ -26,8 +32,10 @@ steps:
       # one-time full wipe to fix corrupted .so files from previous failed builds
       - rm -rf /mnt/cache/R-pkgs
       - mkdir -p /mnt/cache/pkgcache /mnt/cache/R-pkgs /mnt/cache/ccache /mnt/cache/packages
+      - git clone -q https://pat-s:$$REPO_RO_TOKEN@git.devxy.io/devxy/build-cran-binaries.git .
       - git clone -q https://codefloe.com/rpkgs/bincraft.git /tmp/bincraft
       - R -q -e 'pak::cache_clean(); pak::sysreqs_db_update(); pak::local_install("/tmp/bincraft"); pak::pak(c("RPostgres", "s3fs", "data.table", "future")); packageVersion("bincraft")'
+      - R -q -e "source('local/packages-to-build.R'); saveRDS(pkgs, '/mnt/cache/packages/pkgs_to_build.rds'); sprintf('Precomputed %s packages to build', length(pkgs))"
     backend_options:
       docker:
         resources: