fix: update mount dir for opam

Author: BoYanZh

jd4/_sandbox.pyx

@@ -63,7 +63,7 @@ def enter_namespace(root_dir, in_dir, out_dir):
     bind_or_link('/usr/libexec', 'usr/libexec')
     bind_or_link('/usr/share', 'usr/share')
     bind_or_link('/usr/local', 'usr/local', True)
-    bind_or_link('/root/.opam', '.opam', True)
+    bind_or_link('/root/.opam', 'root/.opam', True)
     bind_or_link('/var/lib/ghc', 'var/lib/ghc')
     bind_mount(in_dir, 'in', True, False, True, False)
     bind_mount(out_dir, 'out', True, False, True, False)