Conditionally load MKL_jll based on preference

Author: ChrisRackauckas

src/LinearSolve.jl

@@ -38,24 +38,22 @@ PrecompileTools.@recompile_invalidations begin
 
     # wrap
     import Krylov
-
     using SciMLBase
-
-    using MKL_jll
-
     import Preferences
 end
 
-if Preferences.@load_preference("TriggerMKLLBT", true)
+@static if Preferences.@load_preference("TriggerMKLLBT", true)
+   using MKL_jll
    using MKL
+   const usemkl = MKL_jll.is_available()
+else
+   const usemkl = false
 end
 
 using Reexport
 @reexport using SciMLBase
 using SciMLBase: _unwrap_val
 
-const usemkl = MKL_jll.is_available()
-
 abstract type SciMLLinearSolveAlgorithm <: SciMLBase.AbstractLinearAlgorithm end
 abstract type AbstractFactorization <: SciMLLinearSolveAlgorithm end
 abstract type AbstractKrylovSubspaceMethod <: SciMLLinearSolveAlgorithm end