workaround autoprecompilation warning about instantiating with julia_version

Author: IanButterworth

src/Prefix.jl

@@ -604,15 +604,20 @@ end
 
 # Helper function to install packages also in Julia v1.8
 function Pkg_add(args...; kwargs...)
-    @static if VERSION < v"1.8.0"
-        Pkg.add(args...; kwargs...)
-    else
-        try
-            Pkg.respect_sysimage_versions(false)
+    # auto-precompilation calls `instantiate` which creates `julia_version` related warnings (nothing, or mismatch)
+    # so manually call precompile after adding the packages with `already_instantiated=true` to avoid warnings
+    withenv("JULIA_PKG_AUTO_PRECOMPILE" => "false") do
+        @static if VERSION < v"1.8.0"
             Pkg.add(args...; kwargs...)
-        finally
-            Pkg.respect_sysimage_versions(true)
+        else
+            try
+                Pkg.respect_sysimage_versions(false)
+                Pkg.add(args...; kwargs...)
+            finally
+                Pkg.respect_sysimage_versions(true)
+            end
         end
+        Pkg.precompile(;already_instantiated=true)
     end
 end