NRPy Dendro Apptainer

CPU-only build environment for qualifying NRPy-generated Dendro-GR modules. The official Ubuntu OCI image uses the ubuntu:24.04 tag; the definition upgrades it and refuses to build unless the resulting userspace is Ubuntu 24.04.5.

Build from this directory so %files can find requirements.txt:

cd .dendro_apptainer
apptainer build dendro-ubuntu24.04.5.sif Apptainer.def

The image exports read-only source templates through DENDRO_GR_SOURCE, DENDROLIB_SOURCE, TOML11_SOURCE, and SPDLOG_SOURCE. Copy the two Dendro trees into a writable directory before adding and building generated code. Their shallow Git metadata is retained so a writable copy can fetch other revisions. Upstream documentation and figures are omitted because they are not part of generated-module builds. Supply the cached header-only dependencies during CMake configuration:

-DFETCHCONTENT_SOURCE_DIR_TOML11="$TOML11_SOURCE" \
-DFETCHCONTENT_SOURCE_DIR_SPDLOG="$SPDLOG_SOURCE"