Windows platform: don't allow MakefilePackage (#29904)

lib/spack/spack/build_systems/makefile.py

@@ -10,6 +10,7 @@
 import llnl.util.tty as tty
 from llnl.util.filesystem import working_dir
 
+from spack.directives import conflicts
 from spack.package import PackageBase, run_after
 
 
@@ -55,6 +56,7 @@ class MakefilePackage(PackageBase):
     #: phase
     install_targets = ['install']
 
+    conflicts('platform=windows')
     #: Callback names for build-time test
     build_time_test_callbacks = ['check']