Add integration tests to verify that btf_maps generated with the
generalized btf_map_def macro are compatible with libbpf's bpf_map_def.
Also add CI infrastructure for macOS cross-compilation to Linux musl,
including stub headers and autoconf cache variables for libbpf-sys
vendored dependencies.
Rust CI does not provide dynamic libLLVM tarballs for macOS—only static
ones. Since recent versions of bpf-linker require explicit linkage
configuration for libLLVM, enable the `llvm-link-static` feature to
ensure correct static linking.
Make sure bpf-linker's build.rs sees the downloaded LLVM by adding it
to PATH. On macOS, set the `{CXXSTDLIB,ZLIB}_PATH` variables to point
to the brew prefixes with static libraries it needs.
Given that now we link statically all libLLVM's dependencies and macOS
provides only dynamic zlib, we need to install static zlib from brew.
Bundle handling of Debian kernel archives into xtask so callers can pipe
the raw `.deb` paths straight into `cargo xtask integration-test vm …`.
The driver now extracts each archive into `<cache>/kernel-archives`,
locates the matching `vmlinuz-*`, `lib/modules/*`, and config files, and
feeds those into the initramfs build without requiring the user to
pre-run dpkg/tar. With this in place we drop
`.github/scripts/find_kernels.py`, simplify AGENTS.md/CI instructions to
use `find test/.tmp -name '*.deb'`, remove the gnu-tar requirement we no
longer need, and add `tar` as a workspace dependency for the extractor.
