Add Enzyme GPU support

Fix examples tests with CUDA backend

Add synchronize rule

Author: michel2323

Diff for: Project.toml

@@ -21,7 +21,7 @@ UnsafeAtomicsLLVM = "d80eeb9a-aca5-4d75-85e5-170c8b632249"
 [compat]
 Adapt = "0.4, 1.0, 2.0, 3.0, 4"
 Atomix = "0.1"
-EnzymeCore = "0.7.1"
+EnzymeCore = "0.7.2"
 InteractiveUtils = "1.6"
 LinearAlgebra = "1.6"
 MacroTools = "0.5"

Diff for: examples/utils.jl

@@ -1,5 +1,5 @@
 # EXCLUDE FROM TESTING
-if Base.find_package("CUDA") !== nothing
+if backend_str == "CUDA" && Base.find_package("CUDA") !== nothing
     using CUDA
     using CUDA.CUDAKernels
     const backend = CUDABackend()