Reduce compilation of Base methods (NFC) (JuliaPackaging#38)

This is motivated by JuliaLang/julia#43990 (comment),
but doesn't seem likely to hurt anything even if that never merges.

src/toplevel_generators.jl

@@ -133,10 +133,14 @@ function generate_wrapper_load(src_name, pkg_uuid, __source__)
  # Helper function to parse triplets for us
  $(platform_parse_compat())
  function make_wrapper_dict(dir, x)
- return Dict(
- parse_wrapper_platform(basename(f)[1:end-3]) =>
- joinpath(dir, "wrappers", f) for f in x
- )
+ # (1) make the Dict type inferrable
+ # (2) avoid creation of Generators so that we don't have to compile
+ # package-specific Generator-closures
+ d = Dict{Platform,String}()
+ for f in x
+ d[parse_wrapper_platform(basename(f)[1:end-3])] = joinpath(dir, "wrappers", f)
+ end
+ return d
  end
 
  # If it's a Dict, that means this is an AnyPlatform artifact, act accordingly:
@@ -145,7 +149,10 @@ function generate_wrapper_load(src_name, pkg_uuid, __source__)
  else
  # Otherwise, it's a Vector, and we must select the best platform
  # First, find all wrappers on-disk, parse their platforms, and match:
- wrapper_files = filter(x -> endswith(x, ".jl"), readdir(joinpath($(pkg_dir), "wrappers")))
+ wrapper_files = String[]
+ for x in readdir(joinpath($(pkg_dir), "wrappers"))
+ endswith(x, ".jl") && push!(wrapper_files, x) # avoid creation of Generators...
+ end
  wrappers = make_wrapper_dict($(pkg_dir), wrapper_files)
  for e in artifacts
  platform = unpack_platform(e, $(jll_name), artifacts_toml)