fix: Add patch to add .Makefile.inc to fastjet-contrib

* As each contribution in fastjet-contrib has their own Makefile which
  defines CXX and CXXFLAGS it is necessary to use a globally used
  .Makefile.inc to change these everywhere. For fastjet to be able to
  control the values from the environment that fastjet is being built
  in, use a .Makefile.inc patch to undefine CXX and CXXFLAGS for Make.
  This allows for the environment varaibles to be picked up.
* Remove patch_makefilein.txt as patch_makefileinc.txt supreceeds it.

MANIFEST.in

@@ -4,5 +4,5 @@ graft fastjet-core
 graft fastjet-contrib
 graft pybind11
 global-exclude .git .gitmodules
-include LICENSE README.md pyproject.toml setup.py setup.cfg patch_fastjet_i.txt patch_clustersequence.txt patch_makefilein.txt
+include LICENSE README.md pyproject.toml setup.py setup.cfg patch_fastjet_i.txt patch_clustersequence.txt patch_makefileinc.txt
 exclude .cirrus.yml

patch_makefileinc.txt

@@ -0,0 +1,21 @@
+From 8044976424439224824e4dd265380bb2f750be1a Mon Sep 17 00:00:00 2001
+From: Matthew Feickert <[email protected]>
+Date: Fri, 16 Feb 2024 18:00:36 -0600
+Subject: [PATCH] Add .Makefile.inc for fastjet
+
+---
+ .Makefile.inc | 3 +++
+ 1 file changed, 3 insertions(+)
+ create mode 100644 .Makefile.inc
+
+diff --git a/.Makefile.inc b/.Makefile.inc
+new file mode 100644
+index 0000000..595b3aa
+--- /dev/null
++++ b/.Makefile.inc
+@@ -0,0 +1,3 @@
++# undefine variables defined in Makefile.in and each contrib Makefile
++undefine CXX=g++
++undefine CXXFLAGS=-O2 -Wall -g
+--
+2.34.1

setup.py

@@ -102,7 +102,7 @@ def build_extensions(self):
             subprocess.run(["make", "install"], cwd=FASTJET, env=env, check=True)
 
             subprocess.run(
-                ["patch", "./Makefile.in", DIR / "patch_makefilein.txt"],
+                ["patch", "./.Makefile.inc", DIR / "patch_makefileinc.txt"],
                 cwd=FASTJET_CONTRIB,
                 env=env,
                 check=True,