tools/eclipse: remove infinite loop searching root

In case project.py is invoked with a root which is not a bazel
workspace, it will enter an infinite loop searching for `/WORKSPACE`.

exit immediately after checking `/`.

Change-Id: I2c2e892f121c935136b5449486001a85aa163b2d

tools/eclipse/project.py

diff --git a/tools/eclipse/project.py b/tools/eclipse/project.py
index cbad31e..a24266f 100755
--- a/tools/eclipse/project.py
+++ b/tools/eclipse/project.py
@@ -44,6 +44,10 @@
 root = args.root
 ROOT = os.path.abspath(root)
 while not os.path.exists(os.path.join(ROOT, 'WORKSPACE')):
+  if ROOT == '/':
+    print('Could not find root of project: no WORKSPACE file found',
+          file=sys.stderr)
+    sys.exit(1)
   ROOT = os.path.dirname(ROOT)
 
 batch_option = '--batch' if args.batch else None