put extracted modules behind the switch, to enable doc generation

lib/system.nim

@@ -2926,6 +2926,7 @@ proc compiles*(x: untyped): bool {.magic: "Compiles", noSideEffect, compileTime.
   discard
 
 
+when not defined(nimSlimSystem):
   import system/assertions
   export assertions
 
@@ -3332,7 +3333,7 @@ template unlikely*(val: bool): bool =
     else:
       unlikelyProc(val)
 
-
+when not defined(nimSlimSystem):
   import system/dollars
   export dollars
 
@@ -4345,10 +4346,10 @@ when defined(nimHasDefault):
   proc default*(T: typedesc): T {.magic: "Default", noSideEffect.}
     ## returns the default value of the type ``T``.
 
+when not defined(nimSlimSystem):
   import system/widestrs
   export widestrs
 
-when not defined(nimnoio):
   import system/io
   export io
 

lib/system/assertions.nim.cfg

@@ -0,0 +1,2 @@
+--define:nimSlimSystem
+

lib/system/dollars.nim.cfg

@@ -0,0 +1 @@
+--define:nimSlimSystem

lib/system/io.nim.cfg

@@ -1 +1 @@
---define: nimnoio
+--define:nimSlimSystem

lib/system/iterators.nim.cfg

@@ -0,0 +1 @@
+--define:nimSlimSystem

lib/system/widestrs.nim.cfg

@@ -0,0 +1 @@
+--define:nimSlimSystem