koch boot: use different nimcaches for release and debug builds

koch.nim

@@ -244,11 +244,13 @@ proc boot(args: string) =
   var finalDest = "bin" / "nim".exe
   # default to use the 'c' command:
   let bootOptions = if args.len == 0 or args.startsWith("-"): "c" else: ""
+  let smartNimcache = if "release" in args: "rnimcache" else: "dnimcache"
 
   copyExe(findStartNim(), 0.thVersion)
   for i in 0..2:
     echo "iteration: ", i+1
-    exec i.thVersion & " $# $# compiler" / "nim.nim" % [bootOptions, args]
+    exec i.thVersion & " $# $# --nimcache:$# compiler" / "nim.nim" % [bootOptions, args,
+        smartNimcache]
     if sameFileContent(output, i.thVersion):
       copyExe(output, finalDest)
       echo "executables are equal: SUCCESS!"