bugfix

    auto files = split_words(expanded);

    for (const auto& f : files) {

        std::string path = f;

        if (!fs::path(path).is_absolute() && !mf.base_dir.empty()) {

        // GNU make always resolves a relative include path against the

        // process's current working directory, never against the directory

        // of the makefile containing the include -- unlike C's #include,

        // make has no notion of "relative to this file" unless a makefile

        // builds that path itself (e.g. $(dir $(lastword $(MAKEFILE_LIST)))).

        // Falling back to base_dir only when the CWD-relative path doesn't

        // exist is a convenience for genuinely makefile-relative sibling

        // files; trying it FIRST is wrong and dangerous, since it lets an

        // unrelated same-named file elsewhere in the tree silently shadow

        // the real one (confirmed: tools/build/Makefile.build's own

        // "-include $(dir)/Build" -- dir set to "." via the recursive

        // per-directory $(build)=NAME convention -- picked up tools/build/

        // Build, the Makefile.build's own directory, instead of the real

        // CWD-relative tools/lib/subcmd/Build, because tools/build/Build

        // happens to also exist (it builds the unrelated fixdep host tool)

        // -- silently starving tools/lib/subcmd's obj-y and corrupting the

        // objtool build).

        if (!fs::exists(path) && !fs::path(path).is_absolute() && !mf.base_dir.empty()) {

            std::string candidate = mf.base_dir + "/" + path;

            if (fs::exists(candidate)) path = candidate;

        }