Host file disclosure via symlink traversal

Path traversal in Apple container before 1.2.0 allows remote authenticated users to read host files via crafted build-context file requests. In BuildFSSync.read() and BuildFSSync.info() in Sources/ContainerBuild/BuildFSSync.swift, the host checks whether a requested name is lexically inside the build context but then serves the file that the name resolves to, so a symlink inside the context can escape the context root. Exploitation requires a malicious builder peer and a build context containing an out-of-context symlink; the documented consequence is host file disclosure rather than modification or service interruption.