Handle possible trailing '/' in xcode-select output. Patch by Jeff Olson.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@206752 91177308-0d34-0410-b5e6-96231b3b80d8

tools/scan-build/set-xcode-analyzer

@@ -100,7 +100,7 @@ def main():
   if (xcode_path.find(".app/") != -1):
     # Cut off the 'Developer' dir, as the xcspec lies in another part
     # of the Xcode.app subtree.
-    xcode_path = os.path.dirname(xcode_path)
+    xcode_path = xcode_path.rsplit('/Developer', 1)[0]
 
   foundSpec = False
   for x in FindClangSpecs(xcode_path):