clingo: fix build with Python 3.12 (#40154)

var/spack/repos/builtin/packages/clingo/package.py

@@ -42,6 +42,7 @@ class Clingo(CMakePackage):
     # See https://github.com/potassco/clingo/blob/v5.5.2/INSTALL.md
     depends_on("cmake@3.1:", type="build")
     depends_on("cmake@3.18:", type="build", when="@5.5:")
+    depends_on("py-setuptools", when="@5.6.2:", type="build")
 
     depends_on("doxygen", type="build", when="+docs")
 
@@ -68,6 +69,12 @@ class Clingo(CMakePackage):
     patch("size-t.patch", when="%msvc")
     patch("vs2022.patch", when="%msvc@19.30:")
 
+    # TODO: Simplify this after Spack 0.21 release. The old concretizer has problems with
+    # py-setuptools ^python@3.6, so we only apply the distutils -> setuptools patch for Python 3.12
+    with when("@:5.6.1 ^python@3.12:"):
+        patch("setuptools.patch")
+        depends_on("py-setuptools", type="build")
+
     def patch(self):
         # Doxygen is optional but can't be disabled with a -D, so patch
         # it out if it's really supposed to be disabled

var/spack/repos/builtin/packages/clingo/setuptools.patch

@@ -0,0 +1,14 @@
+diff --git a/cmake/python-site.py b/cmake/python-site.py
+index 1e7fc8ce..95ef827f 100644
+--- a/cmake/python-site.py
++++ b/cmake/python-site.py
+@@ -1,4 +1,7 @@
+-from distutils.sysconfig import get_python_lib, get_config_vars
++try:
++    from setuptools.sysconfig import get_python_lib, get_config_vars
++except ImportError:
++    from distutils.sysconfig import get_python_lib, get_config_vars
+ import sys
+ if sys.argv[1] == "prefix":
+     print(get_python_lib(True, False, sys.argv[2] if len(sys.argv) > 2 else None))
+