Import ospaths instead of include (#5233)

* Import ospaths instead of include
* searchExtPos made public

lib/pure/os.nim

@@ -26,7 +26,8 @@ elif defined(posix):
 else:
   {.error: "OS module not ported to your operating system!".}
 
-include ospaths
+import ospaths
+export ospaths
 
 when defined(posix):
   when NoFakeVars:
@@ -848,12 +849,12 @@ template walkCommon(pattern: string, filter) =
     res = findFirstFile(pattern, f)
     if res != -1:
       defer: findClose(res)
+      let dotPos = searchExtPos(pattern)
       while true:
         if not skipFindData(f) and filter(f):
           # Windows bug/gotcha: 't*.nim' matches 'tfoo.nims' -.- so we check
           # that the file extensions have the same length ...
           let ff = getFilename(f)
-          let dotPos = searchExtPos(pattern)
           let idx = ff.len - pattern.len + dotPos
           if dotPos < 0 or idx >= ff.len or ff[idx] == '.' or
               pattern[dotPos+1] == '*':
@@ -1109,7 +1110,7 @@ proc createDir*(dir: string) {.rtl, extern: "nos$1",
   ## fail if the directory already exists because for most usages this does not
   ## indicate an error.
   var omitNext = false
-  when doslike:
+  when doslikeFileSystem:
     omitNext = isAbsolute(dir)
   for i in 1.. dir.len-1:
     if dir[i] in {DirSep, AltSep}: