[legacy] boost: Backport support for Numpy 2

see boostorg/python#431

fix FairRootGroup#550

cmake/legacy.cmake

@@ -166,6 +166,7 @@ ExternalProject_Add(boost
   URL "https://boostorg.jfrog.io/artifactory/main/release/1.${boost_version}.0/source/boost_1_${boost_version}_0.tar.bz2"
   URL_HASH SHA256=6478edfe2f3305127cffe8caf73ea0176c53769f4bf1585be237eb30798c3b8e
   BUILD_IN_SOURCE ON
+  PATCH_COMMAND ${patch} -d libs/python -p1 -i "${CMAKE_SOURCE_DIR}/legacy/boost/support-numpy-2.patch"
   CONFIGURE_COMMAND "./bootstrap.sh"
     "--prefix=${CMAKE_INSTALL_PREFIX}"
     ${boost_python_config_bootstrap}

legacy/boost/support-numpy-2.patch

@@ -0,0 +1,28 @@
+From 33ac06ca59a68266d3d26edf08205d31ddab4a6c Mon Sep 17 00:00:00 2001
+From: Alexis DUBURCQ <[email protected]>
+Date: Fri, 15 Mar 2024 14:10:16 +0100
+Subject: [PATCH] Support numpy 2.0.0b1
+
+---
+ src/numpy/dtype.cpp | 8 +++++++-
+ 1 file changed, 7 insertions(+), 1 deletion(-)
+
+diff --git a/src/numpy/dtype.cpp b/src/numpy/dtype.cpp
+index 88a20a27b5..da30d1927b 100644
+--- a/src/numpy/dtype.cpp
++++ b/src/numpy/dtype.cpp
+@@ -98,7 +98,13 @@ python::detail::new_reference dtype::convert(object const & arg, bool align)
+   return python::detail::new_reference(reinterpret_cast<PyObject*>(obj));
+ }
+
+-int dtype::get_itemsize() const { return reinterpret_cast<PyArray_Descr*>(ptr())->elsize;}
++int dtype::get_itemsize() const {
++#if NPY_ABI_VERSION < 0x02000000
++  return reinterpret_cast<PyArray_Descr*>(ptr())->elsize;
++#else
++  return PyDataType_ELSIZE(reinterpret_cast<PyArray_Descr*>(ptr()));
++#endif
++}
+
+ bool equivalent(dtype const & a, dtype const & b) {
+     // On Windows x64, the behaviour described on