With the `enable-patchelf` build attribute, `patch_elf()` picked the dynamic linker and the library arch triplet with `platform.machine()`, which is the build host. When cross-compiling, for example on arm64 for armhf, binaries got the arm64 interpreter (`ld-linux-aarch64.so.1`), which doesn't exist on the target. Changes: - `elf_utils.get_dynamic_linker()` takes an optional `arch` argument, like `get_arch_triplet()` already does. The linker's standard path is also available from a new `get_dynamic_linker_path()` helper. - `patch_elf()` uses the build-for architecture for the linker and for the arch triplet used to look up libraries. - If the linker isn't staged and the build is cross-compiling, `patch_elf()` uses the linker's standard location in the base snap instead of checking the host. Cross toolchains like `gcc-arm-linux-gnueabihf` (used by the snap in the issue) install the target's linker under `/usr/<triplet>/`, so checking the host would fail even though the base snap provides the linker at runtime. Native builds behave as before. `test_post_prime_patchelf` only runs when `patchelf` is installed, and its mocked step info needed `arch_build_for` and `is_cross_compiling`, so I added them. Fixes #5836 --- - [x] I've followed the [contribution guidelines](https://github.com/canonical/snapcraft/blob/main/CONTRIBUTING.md). - [x] I've signed the [CLA](http://www.ubuntu.com/legal/contributors/). - [x] I've successfully run `make lint && make test`. - [ ] I've added or updated any relevant documentation. - [ ] In documents I changed, I [added a meta description](https://canonical-starflow.readthedocs-hosted.com/how-to/add-a-page-meta-description/) if one was missing. - [ ] I've updated the relevant release notes.