Adapt nlohmann pipeline to check s-core matrix specification

The nlohmann pipelines should be checked if they cover all s-core specifications and the pipelines should be adjusted if necessary.
In the score-tech-leads-circle-public channel, the following information regarding a matrix specification was provided (28 July 2025):
- These target platforms: https://github.com/eclipse-score/bazel_platforms/blob/main/BUILD
- Feel free to contribute to that discussions but for now not specified
- For the compiler versions we should use the toolchain repos:
- GCC: https://github.com/eclipse-score/toolchains_gcc/blob/main/README.md)
- QNX toolchain for x86_64 and aarch64: https://github.com/eclipse-score/toolchains_qnx