ANDROID: add .bazelignore file

tools/testing/kunit/kunit.py generates .kunit/ folder. The contents
inside the folder break building with bazel.

Bug: 296486873
Test: presubmit
Signed-off-by: Cheng-Cheng Lo <locc@google.com>
(cherry picked from https://android-review.googlesource.com/q/commit:6ce0e9e8ca4babbc9e47fa5e67e8a72998594d52)
Merged-In: Ib00bec343e54f89619bbbaf80d086a233d89e4d2
Change-Id: Ib00bec343e54f89619bbbaf80d086a233d89e4d2

.bazelignore

+common/.kunit