Make the python install prefix conform to python conventions

python/CMakeLists.txt

@@ -1,4 +1,20 @@
-install(DIRECTORY edm4hep DESTINATION python
+find_package(Python3 REQUIRED)
+
+# Setup the python install dir. See the discussion in
+# https://github.com/AIDASoft/podio/pull/599 for more details on why this is
+# done the way it is
+set(edm4hep_python_lib_dir lib)
+if("${Python3_SITEARCH}" MATCHES "/lib64/")
+  set(edm4hep_python_lib_dir lib64)
+endif()
+
+set(EDM4HEP_PYTHON_INSTALLDIR
+  "${CMAKE_INSTALL_PREFIX}/${edm4hep_python_lib_dir}/python${Python3_VERSION_MAJOR}.${Python3_VERSION_MINOR}/site-packages"
+  CACHE STRING
+  "The install prefix for the python bindings"
+)
+
+install(DIRECTORY edm4hep DESTINATION ${EDM4HEP_PYTHON_INSTALLDIR}
   REGEX .*\\.in EXCLUDE
   PATTERN __pycache__ EXCLUDE
 )