delay loading of Pkg until necessary

Author: vchuravy

src/toplevel_generators.jl

@@ -41,7 +41,6 @@ function generate_imports(src_name)
             using Libdl, Artifacts, JLLWrappers.Preferences, Base.BinaryPlatforms
             using Artifacts: load_artifacts_toml, unpack_platform
             using Base.BinaryPlatforms: triplet, select_platform
-            import Pkg
             if !@isdefined(augment_platform!)
                 augment_platform!(platform) = platform
             end
@@ -81,7 +80,6 @@ This method generates the toplevel definitions common to all JLL packages, such
 `is_available()`, the `PATH` and `LIBPATH` symbols, etc....
 """
 function generate_toplevel_definitions(src_name, __source__)
-    pkg_dir = dirname(String(__source__.file))
     return quote
         """
             is_available()
@@ -172,7 +170,9 @@ function generate_wrapper_load(src_name, pkg_uuid, __source__)
         end
 
         if VERSION >= v"1.6"
-            function ensure_artifact_installed(platform=host_platform)
+            function install_current_artifact(platform=host_platform)
+                # Avoid loading Pkg by default, to keep the latency down if we can
+                local Pkg = Base.require(Base.PkgId(UUID((0x44cfe95a_1eb2_52ea, 0xb672_e2afdf69b78f)), "Pkg"))
                 Pkg.Artifacts.ensure_artifact_installed($(src_name), joinpath($(pkg_dir), "..", "Artifacts.toml"); platform=platform, pkg_uuid=$(pkg_uuid))
             end
         end

src/wrapper_generators.jl

@@ -29,7 +29,7 @@ macro generate_wrapper_header(src_name)
                 catch
                     # 1.6 does not call `.pkg/select_artifacts.jl`
                     # 1.7+ User might switch the tag, without calling `Pkg.instantiate()`
-                    ensure_artifact_installed(host_platform)
+                    install_current_artifact(host_platform)
                     return find_artifact_dir()
                 end
             end