[git] Add .gitignore, ignore .cipd/ and .build-id/

.cipd/ is an internal directory managed by the cipd client which
shouldn't be included in the repo.

.build-id/ should potentially be in the repo (?) but it's way too big
and it would be best to exclude debug binaries for the sake of the
checkout time until we're absolutely sure we need them.

Bug: 120912
Change-Id: I12a3af01785bded02c0f3bf04072edcc0e07c97c
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia-bazel-rules/+/799762
Fuchsia-Auto-Submit: Anthony Fandrianto <atyfto@google.com>
Reviewed-by: Oliver Newman <olivernewman@google.com>
Commit-Queue: Anthony Fandrianto <atyfto@google.com>
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..3a67557
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+# Ignore internal CIPD directories.
+.cipd/
+
+# TODO: Debug symbols are too large and should be excluded from the CIPD package
+# itself. Then remove this line.
+.build-id/