feat: add AMD GPU (amdflang/OpenMP offload) container

[sbryngelson]

Summary

• Dockerfile: adds TARGET=amd branch — downloads AFAR drop (rocm-afar-8873-drop-22.2.0) from repo.radeon.com, installs cmake 3.28 (Ubuntu 22.04 ships 3.22 which doesn't recognise LLVMFlang), builds MPICH 3.4.3 with amdflang as the Fortran compiler so mpi.mod is compiler-compatible, and includes libnuma1/libdrm2/libdrm-amdgpu1 so only --rocm is needed at Apptainer runtime
• docker.yml: adds amd matrix entry with full build/push/manifest steps; $TAG-amd manifest always, latest-amd on release only
• CMakeLists.txt: makes Cray-specific MPI/hipfft paths conditional on CRAY_MPICH_INC/CRAY_HIPFORT_LIB being set; falls back to standard find_package(MPI) and find_library(hipfft/amdhip64) with $OLCF_AFAR_ROOT hints so the self-contained container works without any OLCF env vars loaded
• toolchain: adds amd90a cluster profile (HPCFund gfx90a / MI250); fixes module variable export loop so vars that reference previously exported vars expand in the right order

Validation

• Built mfc-amd-final.sif (Apptainer) on top of Ubuntu 22.04 + AFAR + cmake 3.28 + MPICH 3.4.3
• All 32 dry-run tests passed
• 1D Sod shock tube ran 1001 time steps on MI250X (gfx90a) GPU via apptainer exec --writable-tmpfs --rocm

Test plan

• Docker CI build passes for TARGET=amd (compile + dry-run, no GPU runner needed in CI)
• Existing cpu and gpu builds unaffected
• latest-amd manifest pushed only on release trigger

[github-actions]

Claude Code Review

Head SHA: 1557fc4

Files changed:

• 5
• .github/Dockerfile
• .github/workflows/docker.yml
• CMakeLists.txt
• toolchain/bootstrap/modules.sh
• toolchain/modules

Findings:

1. OLCF_AFAR_ROOT is set to /opt/ in cpu and gpu Docker images

.github/Dockerfile — the unconditional ENV line after ARG AFAR_VERSION:

ENV OLCF_AFAR_ROOT=/opt/${AFAR_VERSION}

When the AFAR_VERSION build-arg is not supplied (the cpu and gpu matrix entries provide no AFAR_VERSION), Docker expands the ARG as an empty string, producing OLCF_AFAR_ROOT=/opt/. This real system directory is baked into the published cpu and gpu images. CMakeLists.txt uses HINTS "$ENV{OLCF_AFAR_ROOT}/lib" for find_library calls inside the LLVMFlang GPU path; on those images that resolves to /opt/lib, which could yield false positives if a matching library happens to be present there. The fix is to guard the ENV instruction under an ARG-conditional build stage, or give ARG AFAR_VERSION a sentinel default that is guaranteed absent from /opt/.

2. flang_rt.hostdevice removed from Cray CCE GPU (OpenMP) link path

CMakeLists.txt, the changed hunk around line 703–710:

-                find_package(hipfort COMPONENTS hip CONFIG REQUIRED)
-                target_link_libraries(${a_target} PRIVATE hipfort::hip hipfort::hipfort-amdgcn flang_rt.hostdevice)

The post-change Cray block (context lines 704–705) now links only hipfort::hip hipfort::hipfort-amdgcn; flang_rt.hostdevice was moved exclusively to the new elseif(CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang") block. Frontier builds using PrgEnv-cray (compiler ID "Cray") with OpenMP GPU offload previously linked flang_rt.hostdevice. If Cray CCE requires that library for device-code linking on AMD GPUs, this removal is a regression. The change should be validated against a live Frontier build before merging.