Add support for a customizable `.bazelrc.user` file

Sometimes you want to set some options for a specific repo. You
_could_ use `~/.bazelrc`, but that applies to _all_ Bazel projects.
This file allow users to set options for just this repo without
affecting other repos.

This follows the recommendation from Aspect:
https://blog.aspect.dev/bazelrc-flags

> As the very last line in .bazelrc:
>
>    try-import %workspace%/.bazelrc.user: allow developers to add
>    repo-specific overrides in their own personal .bazelrc.user file.
>    Make sure this is git-ignored.

Signed-off-by: Philipp Schrader <philipp.schrader@gmail.com>
Change-Id: I26dbeaf1c4de41a90a1506784d4ab88ea7f48cee
diff --git a/.bazelrc b/.bazelrc
index 7ed7d93..61ac856 100644
--- a/.bazelrc
+++ b/.bazelrc
@@ -112,3 +112,8 @@
 
 # Prevent cypress from using its own binary. We want to use the hermetic one.
 build --action_env=CYPRESS_INSTALL_BINARY=0
+
+# Load a local file that users can use to customize bazel invocations.  This
+# should stay the last line in this file so users can override things when they
+# want.
+try-import %workspace%/.bazelrc.user
diff --git a/.gitignore b/.gitignore
index 3f27e94..f6f3eeb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 *.pyc
 /bazel-*
 /compile_commands.json
+/.bazelrc.user
 
 # The `tools/build_rules/apache_runner.py` helper looks for this file by
 # default. We don't want folks to check it in.