fix #14179, fix #14142, make CI 1.4x faster (2x faster locally) (#14658)

* fix #14142: no more clash with: import os + use of existsDir/dirExists/existsFile/fileExists/findExe in config.nims

* remove a comment

* Revert "fixes the regression #12860 caused; hotfix"

This reverts commit 3d2459bdc0.

* Revert "Undefine `paramCount` & `paramStr` in nimscript.nim for *.nims (#12860)"

This reverts commit d38853c504.

* noNimScript => noWeirdTarget + noNimJs

lib/system/nimscript.nim

@@ -56,6 +56,14 @@ proc rawExec(cmd: string): int {.tags: [ExecIOEffect], raises: [OSError].} =
 proc warningImpl(arg, orig: string) = discard
 proc hintImpl(arg, orig: string) = discard
 
+proc paramStr*(i: int): string =
+  ## Retrieves the ``i``'th command line parameter.
+  builtin
+
+proc paramCount*(): int =
+  ## Retrieves the number of command line parameters.
+  builtin
+
 proc switch*(key: string, val="") =
   ## Sets a Nim compiler command line switch, for
   ## example ``switch("checks", "on")``.
@@ -272,9 +280,6 @@ proc selfExec*(command: string) {.
       raise newException(OSError, "FAILED: " & c)
     checkOsError()
 
-from os import paramCount, paramStr
-export paramCount, paramStr
-
 proc put*(key, value: string) =
   ## Sets a configuration 'key' like 'gcc.options.always' to its value.
   builtin