Allow PyPy to use ROOT (pyroot)

I posted this at https://foss.heptapod.net/pypy/pypy/-/issues/3455,
and they recommended to write to this mailing list.

ROOT data analysis framework (https://root.cern) is written in C++
(with cppyy Python bindings). I tried to import that in PyPy, and got
an error

>>>> import ROOT
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/root/cur/lib/ROOT/__init__.py", line 22, in <module>
    import cppyy
  File "/opt/root/cur/lib/cppyy/__init__.py", line 64, in <module>
    libcppyy_mod_name, major, minor))
ImportError: Failed to import libcppyy2_7. Please check that ROOT has
been built for Python 2.7

However, I allowed support for Python 2 in ROOT, and python2 imports
ROOT fine. That library is in LD_LIBRARY_PATH.

Could you please add support of ROOT in PyPy?