acts: add new dependency on vecmem and autodiff (#26790)

Co-authored-by: Hadrien G. <knights_of_ni@gmx.com>

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

@@ -189,7 +189,12 @@ class Acts(CMakePackage, CudaPackage):
         description="Enable memory profiling using gperftools",
         when="@19.3:",
     )
-    # FIXME: Cannot build SyCL plugin yet as Spack doesn't have SyCL support
+    variant(
+        "sycl",
+        default=False,
+        description="Build the SyCL plugin",
+        when="@1:",
+    )
     variant("tgeo", default=False, description="Build the TGeo plugin", when="+identification")
 
     # Variants that only affect Acts examples for now
@@ -226,8 +231,6 @@ class Acts(CMakePackage, CudaPackage):
     variant("analysis", default=False, description="Build analysis applications in the examples")
 
     # Build dependencies
-    # FIXME: Use spack's vecmem package once there is one
-    # (https://github.com/acts-project/acts/pull/998)
     depends_on("acts-dd4hep", when="@19 +dd4hep")
     depends_on("autodiff @0.6:", when="@17: +autodiff")
     depends_on("autodiff @0.5.11:0.5.99", when="@1.2:16 +autodiff")
@@ -255,6 +258,8 @@ class Acts(CMakePackage, CudaPackage):
     depends_on("py-pytest", when="+python +unit_tests")
     depends_on("root @6.10: cxxstd=14", when="+tgeo @:0.8.0")
     depends_on("root @6.20: cxxstd=17", when="+tgeo @0.8.1:")
+    depends_on("sycl", when="+sycl")
+    depends_on("vecmem@0.4: +sycl", when="+sycl")
 
     # ACTS has been using C++17 for a while, which precludes use of old GCC
     conflicts("%gcc@:7", when="@0.23:")
@@ -316,6 +321,7 @@ def plugin_cmake_variant(plugin_name, spack_variant):
             enable_cmake_variant("MEMORY_PROFILING", "profilemem"),
             example_cmake_variant("PYTHIA8", "pythia8"),
             example_cmake_variant("PYTHON_BINDINGS", "python"),
+            plugin_cmake_variant("SYCL", "sycl"),
             plugin_cmake_variant("TGEO", "tgeo"),
             cmake_variant(unit_tests_label, "unit_tests"),
         ]