Use conditional for cmake build_system

Author: kwryankrattiger

repos/spack_repo/builtin/packages/libxslt/package.py

@@ -2,8 +2,8 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
-from spack_repo.builtin.build_systems.autotools import AutotoolsPackage, AutotoolsBuilder
-from spack_repo.builtin.build_systems.cmake import CMakePackage, CMakeBuilder
+from spack_repo.builtin.build_systems.autotools import AutotoolsBuilder, AutotoolsPackage
+from spack_repo.builtin.build_systems.cmake import CMakeBuilder, CMakePackage
 
 from spack.package import *
 
@@ -23,7 +23,7 @@ class Libxslt(CMakePackage, AutotoolsPackage):
 
     license("X11", checked_by="wdconinc")
 
-    build_system("cmake", "autotools", default="cmake")
+    build_system(conditional("cmake", when="@:1.1.34"), "autotools", default="cmake")
 
     version("1.1.42", sha256="85ca62cac0d41fc77d3f6033da9df6fd73d20ea2fc18b0a3609ffb4110e1baeb")
     version("1.1.41", sha256="3ad392af91115b7740f7b50d228cc1c5fc13afc1da7f16cb0213917a37f71bda")
@@ -59,9 +59,6 @@ class Libxslt(CMakePackage, AutotoolsPackage):
     depends_on("python+shared", when="+python")
     extends("python", when="+python")
 
-    # CMake was added in version 1.1.35
-    conflicts("build_system=cmake", when="@:1.1.34")
-
     def url_for_version(self, v):
         if v > Version("1.1.34"):
             return f"https://download.gnome.org/sources/libxslt/{v.up_to(2)}/libxslt-{v}.tar.xz"
@@ -101,8 +98,8 @@ def configure_args(self):
 class CMakeBuilder(CMakeBuilder):
     def cmake_args(self):
         return [
-            self.define_from_variant("LIBXSLT_WITH_PYTHON", "+python"),
-            self.define_from_variant("LIBXSLT_WITH_CRYPTO", "+crypto"),
+            self.define_from_variant("LIBXSLT_WITH_PYTHON", "python"),
+            self.define_from_variant("LIBXSLT_WITH_CRYPTO", "crypto"),
             self.define("DLIBXSLT_WITH_MODULES", False),
             self.define("DLIBXSLT_WITH_TESTS", False),
         ]