Tree shaker no longer loads threads into threadless images; 77kb improvement on hello-world size

basis/tools/deploy/shaker/shaker.factor

@@ -13,7 +13,6 @@ QUALIFIED: compiler.errors.private
 QUALIFIED: continuations
 QUALIFIED: definitions
 QUALIFIED: init
-QUALIFIED: io.thread
 QUALIFIED: layouts
 QUALIFIED: listener
 QUALIFIED: prettyprint.config
@@ -214,13 +213,14 @@ IN: tools.deploy.shaker
             continuations:restarts
             listener:error-hook
             init:init-hooks
-            io.thread:io-thread
             source-files:source-files
             input-stream
             output-stream
             error-stream
         } %
 
+        "io-thread" "io.thread" lookup ,
+
         "mallocs" "libc.private" lookup ,
 
         deploy-threads? [

basis/tools/deploy/shaker/strip-debugger.factor

@@ -1,8 +1,14 @@
-USING: kernel threads threads.private ;
+USING: compiler.units words vocabs kernel threads.private ;
 IN: debugger
 
 : print-error ( error -- ) die drop ;
 
 : error. ( error -- ) die drop ;
 
-M: thread error-in-thread ( error thread -- ) die 2drop ;
+"threads" vocab [
+    [
+        "error-in-thread" "threads" lookup
+        [ die 2drop ]
+        define
+    ] with-compilation-unit
+] when