Specify value to --toolchain_resolution_debug (#2141)

[2d25d7fa86666b6e33e65f8a3e27241c88ab36cc](https://github.com/bazelbuild/bazel/commit/2d25d7fa86666b6e33e65f8a3e27241c88ab36cc)
made this an error, so since the Bazel 8 release all RBE builds have
been failing.
diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index c7e78c7..469e45c 100755
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -1923,7 +1923,7 @@
         "--remote_timeout=3600",
         "--incompatible_strict_action_env",
         "--google_default_credentials",
-        "--toolchain_resolution_debug",
+        "--toolchain_resolution_debug=.*",
         "--remote_download_toplevel",
     ]