make sure exe exists

src/main.zig

@@ -1579,6 +1579,11 @@ pub fn main() anyerror!void {
         if (config.zig_exe_path) |exe_path| {
             if (std.fs.path.isAbsolute(exe_path)) {
                 zig_exe_path = try std.mem.dupe(allocator, u8, exe_path);
+                // make sure the path still exists
+                if (blk: {
+                    std.fs.cwd().access(zig_exe_path.?, .{}) catch break :blk false;
+                    break :blk true;
+                })
                     break :find_zig;
             }