bootstrap the compiler with nimPreviewSlimSystem (#20176)

* bootstrap the compiler with nimPreviewSlimSystem

* threads

lib/packages/docutils/dochelpers.nim

@@ -15,6 +15,10 @@
 
 import rstast
 
+when defined(nimPreviewSlimSystem):
+  import std/[assertions, syncio]
+
+
 type
   LangSymbol* = object       ## symbol signature in Nim
     symKind*: string           ## "proc", "const", "type", etc

lib/packages/docutils/highlite.nim

@@ -59,6 +59,10 @@ import
   strutils
 from algorithm import binarySearch
 
+when defined(nimPreviewSlimSystem):
+  import std/assertions
+
+
 type
   SourceLanguage* = enum
     langNone, langNim, langCpp, langCsharp, langC, langJava,

lib/packages/docutils/rst.nim

@@ -238,6 +238,10 @@ import
   std/private/miscdollars, tables, strscans
 from highlite import SourceLanguage, getSourceLanguage
 
+when defined(nimPreviewSlimSystem):
+  import std/[assertions, syncio]
+
+
 type
   RstParseOption* = enum     ## options for the RST parser
     roSupportSmilies,         ## make the RST parser support smilies like ``:)``

lib/packages/docutils/rstast.nim

@@ -11,6 +11,10 @@
 
 import strutils, json
 
+when defined(nimPreviewSlimSystem):
+  import std/assertions
+
+
 type
   RstNodeKind* = enum        ## the possible node kinds of an PRstNode
     rnInner,                  # an inner node or a root

lib/packages/docutils/rstgen.nim

@@ -42,6 +42,11 @@
 import strutils, os, hashes, strtabs, rstast, rst, highlite, tables, sequtils,
   algorithm, parseutils, std/strbasics
 
+
+when defined(nimPreviewSlimSystem):
+  import std/[assertions, syncio]
+
+
 import ../../std/private/since
 
 const