flang, armflang, aocc and tarball nvfortran fail on Ubuntu 26.04 #283

Follow-up to #282 and #281. ubuntu-latest (x64) moves to 26.04 starting 2026-10-19 (actions/runner-images#14748), and these compilers fail there. I ran each on ubuntu-26.04 / ubuntu-26.04-arm on my fork (run 1, run 2); ImageOS is ubuntu26.

Summary of what I found on ubuntu-26.04 (error output, file references and proposed fixes are below the table):

Fails

• flang: src/installers/flang/debian.ts:48 throws Flang is only supported on Ubuntu 22.04 and 24.04 (got: ubuntu26). apt.llvm.org's resolute repo has only LLVM 21–23, so flang 16–20 have no packages.
• armflang: src/installers/armflang/debian.ts:49 throws ArmFlang is only supported on Ubuntu 22.04 and 24.04 (got: ubuntu26-arm64). Arm's resolute repo has only 23.1; 22.1 is missing and the legacy repo for 20.1/21.1 returns 404.
• aocc 5.2: aocc-compiler-5.2.0 depends on libxml2:amd64; however: / Package libxml2 is not installed. at src/installers/aocc/debian.ts:116 (dpkg -i exits non-zero before the apt-get install -f on the next line). The 26.04 archive has libxml2-16 but no libxml2.
• nvfortran from NVIDIA's tarball (20.7, 20.9, and the fallback after an apt failure): tar: ...libcusparse.so.11.1.1.245: Cannot write: Disk quota exceeded. src/installers/nvfortran/debian.ts:297 extracts a multi-GB tarball under os.tmpdir(), and /tmp is now a RAM-backed tmpfs with a ~6.3 GB per-user quota ([Ubuntu 26.04] /tmp is now a RAM-backed tmpfs with a ~7.8G per-user quota; large builds fail with "disk quota exceeded" actions/runner-images#14777, still open).

Works on 26.04: ifx 2026.1, nvfortran 24.3/26.9 (apt path), and on arm gfortran 13, lfortran 0.67.0, nvfortran 24.3.

Proposed fix

• flang/armflang: add a resolute branch to both functions. With that alone, flang 22/23 and armflang 23.1 install and pass the integration tests on 26.04. Versions without resolute packages get an explicit error, like the existing jammy one at flang/debian.ts:169. I have this implemented with unit tests and will open a PR.
• nvfortran: use RUNNER_TEMP instead of os.tmpdir() for the tarball temp dir, as gfortran/debian.ts:33 already does.
• aocc: unpack the .deb with dpkg-deb -x and install its real dependencies through apt instead of using dpkg -i. No binary in the 5.2 package links libxml2, so the declared dependency looks spurious. This passed the integration tests on 26.04 for 5.2 and 4.1 on my fork; 5.1, 5.0 and 4.2 have the same Depends and library requirements (checked offline, not run).
• I'm working on PRs for the flang/armflang, nvfortran and aocc fixes. CI matrix changes are covered by Support ubuntu-26.04 and drop most of ubuntu-22.04? #282.
• I've grouped these because they share one cause and a deadline; if you'd rather track them separately, I'm happy to split this into one issue per compiler. Do you generally prefer related problems grouped in one issue or filed separately?