Test with bazel 6 & 7 in BCR checks

Author: HoloRin

.bcr/presubmit.yml

@@ -6,11 +6,16 @@ shell_commands: &shell_commands
 - ./kerl install ${ERLANG_VERSION} ~/kerl/${ERLANG_VERSION}
 - realpath ~/kerl/${ERLANG_VERSION}
 
+matrix:
+  bazel:
+  - 6.x
+  - 7.x
 platforms:
   macos:
     environment:
       ERLANG_VERSION: "26.2"
       ERLANG_HOME: /Users/buildkite/kerl/26.2
+    bazel: ${{ bazel }}
     shell_commands: *shell_commands
     build_flags:
     - --incompatible_strict_action_env
@@ -20,6 +25,7 @@ platforms:
     environment:
       ERLANG_VERSION: "26.2"
       ERLANG_HOME: /var/lib/buildkite-agent/kerl/26.2
+    bazel: ${{ bazel }}
     shell_commands: *shell_commands
     build_flags:
     - --incompatible_strict_action_env