config system: special case -d:release and -d:danger [backport:1.4] (#18051)

tests/newconfig/tfoo.nim

@@ -1,6 +1,6 @@
 discard """
   cmd: "nim default --hint:cc:off --hint:cc $file"
-  output: '''hello world! 0.5'''
+  output: '''hello world! 0.5 true'''
   nimout: '''[NimScript] exec: gcc -v'''
 """
 
@@ -10,4 +10,4 @@ when not defined(definedefine):
 import math, mfriends
 
 discard gen[int]()
-echo "hello world! ", ln 2.0
+echo "hello world! ", ln 2.0, " ", compileOption("opt", "speed")

tests/newconfig/tfoo.nims

@@ -3,6 +3,8 @@ mode = ScriptMode.Whatif
 
 exec "gcc -v"
 
+--define:release
+
 --forceBuild
 --path: "../friends"