implements experimental new config system based on NimScript

tests/newconfig/tfoo.nim

@@ -0,0 +1,7 @@
+discard """
+  cmd: "nim default $file"
+  output: '''hello world!'''
+  msg: '''[NimScript] exec: gcc -v'''
+"""
+
+echo "hello world!"

tests/newconfig/tfoo.nims

@@ -0,0 +1,14 @@
+
+mode = ScriptMode.Whatif
+
+exec "gcc -v"
+
+--forceBuild
+
+task listDirs, "lists every subdirectory":
+  for x in listDirs("."):
+    echo "DIR ", x
+
+task default, "default target":
+  setCommand "c"
+