make it work on 1.6

Author: vchuravy

test/LAMMPS_jll/.pkg/select_artifacts.jl

@@ -1,6 +1,11 @@
 push!(LOAD_PATH, "..")
 
-using TOML, Artifacts, Base.BinaryPlatforms
+if VERSION < v"1.7"
+    using Pkg.TOML
+else
+    using TOML
+end
+using Artifacts, Base.BinaryPlatforms
 include("./platform_augmentation.jl")
 artifacts_toml = joinpath(dirname(@__DIR__), "Artifacts.toml")