Bazel: Allow user-specific `user.bazelrc` in workspace root

As described in: [1] it's considered to be a best practice allowing a
user-specific `user.bazelrc` in a workspace. See also: [2] for more
details.

[1] https://docs.bazel.build/versions/master/best-practices.html
[2] https://bazel.build/run/bazelrc#imports

Release-Notes: Support Bazel user configuration file in gerrit tree
Change-Id: Ia20a75259758c0924f4c04b08b888ec207d3ff68
diff --git a/.bazelrc b/.bazelrc
index fe7d6dc..a5603ca 100644
--- a/.bazelrc
+++ b/.bazelrc
@@ -50,3 +50,6 @@
 test --test_output=errors
 
 import %workspace%/tools/remote-bazelrc
+
+# User-specific .bazelrc
+try-import %workspace%/user.bazelrc