std.heap.DebugAllocator with .safety = true broken on freestanding targets #25978

const GPA = std.heap.DebugAllocator(.{
    .never_unmap = true,
    .backing_allocator_zeroes = false,
});

fn nullAllocator() std.mem.Allocator {
    return .{ .ptr = undefined, .vtable = undefined };
}
pub const os = struct {
    pub const heap = struct {
        // NEVER USE THIS! This is just to stop it from defaulting fields to POSIX page allocator
        //  DebugAllocator should have its .backing_allocator explicitly set to something else.
        pub const page_allocator = nullAllocator();
    };
};

std\posix.zig:3270:18: error: struct 'posix.system__struct_2784' has no member named 'isatty'
    return system.isatty(handle) != 0;
           ~~~~~~^~~~~~~
std\posix.zig:49:13: note: struct declared here
    else => struct {
            ^~~~~~
referenced by:
    isTty: std\fs\File.zig:130:24
    supportsAnsiEscapeCodes: std\fs\File.zig:242:19
    getOrEnableAnsiEscapeSupport: std\fs\File.zig:220:40
    detect: std\Io\tty.zig:58:46
    detectConfig: std\Io\tty.zig:10:19
    free: std\heap\debug_allocator.zig:938:67
    allocator: std\heap\debug_allocator.zig:344:22