rebuild-toolchain fails while building Jakt support libs: attempts to read AK/Math directory as a file

# The issue Running `Meta/serenity.sh rebuild-toolchain` on the latest `master` fails during the "build jakt support libs" step. The Jakt compiler itself builds and installs successfully. The failure occurs afterwards while building the support libraries. The reported error is: `Runtime error: Operation not permitted (errno=1)` However, tracing the process with `strace` shows the actual failure is: openat(.../Toolchain/Local/jakt/include/runtime/AK/Math, O_RDONLY) fstat(...) = S_IFDIR read(...) = -1 EISDIR (Is a directory) It appears the support-library build is trying to copy `AK/Math` as a regular file even though it is a directory. `AK/Math` exists in the source tree as a directory containing headers. This does not appear to be a filesystem permission problem. # Steps to reproduce: 1. Clone SerenityOS. 2. Run `Meta/serenity.sh rebuild-toolchain` 3. Wait until the "build jakt support libs" step. # Expected behavior: The toolchain builds successfully. # Actual behavior: The build stops with: `Runtime error: Operation not permitted (errno=1)` during the "build jakt support libs" stage. # Host environment OS: Ubuntu 24.04 LTS (Noble Numbat) Filesystem: ext4 Build command: `Meta/serenity.sh rebuild-toolchain` SerenityOS revision: c2572f33914c1e18ec289f207026417b107d9ba7