REPL: only load stdlibs during precompilation script (#57940)

Fixes #57939

Not tested as it's quite involved... requires building a custom
sysimage.

Author: IanButterworth

stdlib/REPL/src/precompile.jl

@@ -6,7 +6,7 @@ module Precompile
 import ..REPL
 # Prepare this staging area with all the loaded packages available
 for (_pkgid, _mod) in Base.loaded_modules
-    if !(_pkgid.name in ("Main", "Core", "Base", "REPL"))
+    if !(_pkgid.name in ("Main", "Core", "Base", "REPL")) && Base.is_stdlib(_pkgid)
         eval(:(const $(Symbol(_mod)) = $_mod))
     end
 end