Search additional paths to find icecube includes for cvmfs icetray: …

…check if these exist first

setup.py

@@ -67,13 +67,14 @@ def get_icecube_includes():
     # get include paths for GitHub icetray builds in cvmfs
     # get directory parts before and after software system
     dir_parts = os.environ['I3_SRC'].split('/metaprojects/')
-    # remove the specified software system
-    prefix = os.path.dirname(dir_parts[0])
-    cvmfs_src_dir = os.path.join(prefix, 'metaprojects', dir_parts[1])
-    include_pattern = os.path.join(cvmfs_src_dir, '*/public')
-    include_dirs.extend(glob.glob(include_pattern))
-    include_dirs.append(os.path.join(
-        cvmfs_src_dir, 'cmake/tool-patches/common/'))
+    if len(dir_parts) > 1:
+        # remove the specified software system
+        prefix = os.path.dirname(dir_parts[0])
+        cvmfs_src_dir = os.path.join(prefix, 'metaprojects', dir_parts[1])
+        include_pattern = os.path.join(cvmfs_src_dir, '*/public')
+        include_dirs.extend(glob.glob(include_pattern))
+        include_dirs.append(os.path.join(
+            cvmfs_src_dir, 'cmake/tool-patches/common/'))
 
     return include_dirs