[Docs] Document Bazel test_filter support

Explain that Unity honors TESTBRIDGE_TEST_ONLY when
UNITY_USE_COMMAND_LINE_ARGS is enabled and that UNITY_GETENV
can be overridden to avoid <stdlib.h>.

Author: tragisch

docs/UnityChangeLog.md

@@ -18,6 +18,7 @@ Prior to 2008, the project was an internal project and not released to the publi
 New Features:
 
   - Add `-n` comand line option as strict matcher again
+  - Support `TESTBRIDGE_TEST_ONLY` for Bazel `--test_filter` when `UNITY_USE_COMMAND_LINE_ARGS` is enabled
 
 Significant Bugfixes:
 

docs/UnityHelperScriptsGuide.md

@@ -231,6 +231,11 @@ These are the available options:
 | `-v`      | increase Verbosity                                |
 | `-x NAME` | eXclude tests whose name includes NAME            |
 
+Unity also supports the `TESTBRIDGE_TEST_ONLY` environment variable (used by
+Bazel's `--test_filter`) when `UNITY_USE_COMMAND_LINE_ARGS` is enabled.
+If you prefer to avoid including `<stdlib.h>`, define `UNITY_GETENV` to your
+own `getenv`-compatible function (for example, via `unity_config.h`).
+
 ##### `:setup_name`
 
 Override the default test `setUp` function name.