CI fails on develop branch

[nlohmann]

Description

There are a few failing tests:

• Clang-Analyze: the recently released Clang 21.0 fails with a -Wmissing-noreturn.
• Clang 8: the runner fails running apt-get update

Reproduction steps

Run a CI (see https://github.com/nlohmann/json/actions/runs/16579251921?pr=4867)

Expected vs. actual results

Green CI

Minimal code example

N/A

Error messages

See logs in https://github.com/nlohmann/json/actions/runs/16579251921?pr=4867

Compiler and operating system

Clang 21

Library version

develop

Validation

• The bug also occurs if the latest version from the develop branch is used.
• I can successfully compile and run the unit tests.

[nlohmann]

Related: #4875