Using .dlext directly from Libdl rather than Base.Libc (#142)

This line broke for me when using ClarabelRs on Julia 1.11.

In previous releases of Julia it seems at you could dlext from Base.Libc.dlext, but that is not the case on 1.11 (at least on macOS). Since Libdl is loaded here one can instead get dlext from Libdl.dlext.

src/julia/ClarabelRs/src/ClarabelRs.jl

@@ -13,7 +13,7 @@ module ClarabelRs
         # > cargo build --release --features julia
         global libpath = joinpath(@__DIR__, 
                         "../../../../target/release/",
-                        "libclarabel." * Base.Libc.dlext
+                        "libclarabel." * Libdl.dlext
                 )
         global librust = Libdl.dlopen(libpath)
     end