move out Distributed from the sysimage (#49258)

src/Distributed.jl

@@ -107,6 +107,7 @@ include("macros.jl")      # @spawn and friends
 include("workerpool.jl")
 include("pmap.jl")
 include("managers.jl")    # LocalManager and SSHManager
+include("precompile.jl")
 
 function __init__()
     init_parallel()

src/precompile.jl

@@ -0,0 +1,14 @@
+precompile(Tuple{typeof(Distributed.remotecall),Function,Int,Module,Vararg{Any, 100}})
+precompile(Tuple{typeof(Distributed.procs)})
+precompile(Tuple{typeof(Distributed.finalize_ref), Distributed.Future})
+# This is disabled because it doesn't give much benefit
+# and the code in Distributed is poorly typed causing many invalidations
+# TODO: Maybe reenable now that Distributed is not in sysimage.
+#=
+    precompile_script *= """
+    using Distributed
+    addprocs(2)
+    pmap(x->iseven(x) ? 1 : 0, 1:4)
+    @distributed (+) for i = 1:100 Int(rand(Bool)) end
+    """
+=#

test/distributed_exec.jl

@@ -1874,7 +1874,7 @@ let julia = `$(Base.julia_cmd()) --startup-file=no`; mktempdir() do tmp
     using Distributed
     project = mktempdir()
     env = Dict(
-        "JULIA_LOAD_PATH" => LOAD_PATH[1],
+        "JULIA_LOAD_PATH" => string(LOAD_PATH[1], $(repr(pathsep)), "@stdlib"),
         "JULIA_DEPOT_PATH" => DEPOT_PATH[1],
         "TMPDIR" => ENV["TMPDIR"],
     )
@@ -1884,7 +1884,7 @@ let julia = `$(Base.julia_cmd()) --startup-file=no`; mktempdir() do tmp
     """ * setupcode * """
     for w in workers()
         @test remotecall_fetch(depot_path, w)          == [DEPOT_PATH[1]]
-        @test remotecall_fetch(load_path, w)           == [LOAD_PATH[1]]
+        @test remotecall_fetch(load_path, w)           == [LOAD_PATH[1], "@stdlib"]
         @test remotecall_fetch(active_project, w)      == project
         @test remotecall_fetch(Base.active_project, w) == joinpath(project, "Project.toml")
     end