Icon Svg export.py: Make id to dir conversion work on Linux

Still works on Windows.

Change-Id: Ic16618b7d57d9d2f9d3c6d817c20eb4860dd1e22
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/tools/icons/export.py

@@ -74,7 +74,8 @@ def pngName(svgID, scale):
 def checkDirectories(svgIDs):
     invalidDirectories = []
     for id in svgIDs:
-        if not os.path.isdir(os.path.join(qtcRoot(), id, '../')):
+        dirForId = os.path.abspath(os.path.join(qtcRoot(), id, os.pardir))
+        if not os.path.isdir(dirForId):
             invalidDirectories.append(id)
 
     if invalidDirectories: