bazel: Support --output_base

A workaround for https://github.com/bazelbuild/bazel/issues/13951 that
allows setting `--output_base=outbazel` while building with Bazel.

Change-Id: Ie024fff2a145f57d3767c270c512b1f3d110d9f8
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/131612
Reviewed-by: Anthony DiGirolamo <tonymd@google.com>
Commit-Queue: Ted Pudlik <tpudlik@google.com>
diff --git a/.bazelignore b/.bazelignore
index 280ad54..5b3b096 100644
--- a/.bazelignore
+++ b/.bazelignore
@@ -4,3 +4,8 @@
 environment
 node_modules
 out
+bazel-bin
+bazel-out
+bazel-pigweed
+bazel-testlogs
+outbazel
diff --git a/.gitignore b/.gitignore
index f06c43c..ed3ae36 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@
 compile_commands.json
 out/
 bazel-*
+outbazel/
 .presubmit/
 docs/_build