Fix builtin lua function os.tempfolder (#7368)

* Fix builtin lua function os.tempfolder

Author: nOOb3167

builtin/mainmenu/common.lua

@@ -172,14 +172,9 @@ os.tempfolder = function()
 	os.remove(filetocheck)
 
 	local randname = "MTTempModFolder_" .. math.random(0,10000)
-	if DIR_DELIM == "\\" then
-		local tempfolder = os.getenv("TEMP")
-		return tempfolder .. filetocheck
-	else
-		local backstring = filetocheck:reverse()
-		return filetocheck:sub(0,filetocheck:len()-backstring:find(DIR_DELIM)+1) ..randname
-	end
-
+	local backstring = filetocheck:reverse()
+	return filetocheck:sub(0, filetocheck:len() - backstring:find(DIR_DELIM) + 1) ..
+		randname
 end
 
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