[BUG] unknown instruction error when adding commands in CRAN builds

Getting error when providing command in CRAN build ``` 2026-01-13 06:36:31.409 | #1 [internal] load build definition from Containerfile 2026-01-13 06:36:31.410 | #1 transferring dockerfile: 539B 0.0s done 2026-01-13 06:36:31.410 | #1 DONE 0.0s 2026-01-13 06:36:31.416 | Containerfile:10 2026-01-13 06:36:31.416 | -------------------- 2026-01-13 06:36:31.416 | 8 | USER root 2026-01-13 06:36:31.416 | 9 | ENV R_LIBS_USER="/usr/local/lib/R/site-library" 2026-01-13 06:36:31.416 | 10 | >>> apt-get update 2026-01-13 06:36:31.416 | 11 | apt-get install -y libcurl4-openssl-dev 2026-01-13 06:36:31.416 | 12 | 2026-01-13 06:36:31.416 | -------------------- 2026-01-13 06:36:31.416 | error: failed to solve: dockerfile parse error on line 10: unknown instruction: apt-get ``` Reproducer ``` curl --location 'https://wave.seqera.io/v1alpha2/container' \ --header 'Content-Type: application/json' \ --data '{ "packages": { "type": "CRAN", "entries": [ "dplyr", "ggplot2", "bioc::GenomicRanges" ], "channels": [ "cran", "bioconductor" ], "cranOpts": { "rImage": "rocker/r-ver:4.4.1", "basePackages": "littler r-cran-docopt", "commands": [ "apt-get update", "apt-get install -y libcurl4-openssl-dev" ] } }, "format": "d", "containerPlatform": "linux/amd64" }' ``` detailed build: https://wave.seqera.io/view/builds/bd-52cc233dfe45b950_1