Check for yum presence rather than rely on CI tags

From the looks of it, the CI_RUNNER_TAGS format may have changed to be '["tag1", "tag2"]' so doing the actual check will not work.

Hence rather than relying on this environment variable content and format, check whether yum is present on the runner and use it if so.

This fixes the issue from beat/beat.editor> pipelines not running because there are now missing packages.

bob/devtools/scripts/build.py

@@ -247,11 +247,12 @@ def build(
         if not os.path.exists(d):
             raise RuntimeError("The directory %s does not exist" % d)
 
-        # If in docker, install the packages inside the yum_requirements.txt file if it exists
+        # If using RH based image/runner, install the packages inside the
+        # yum_requirements.txt file if it exists
         yum_requirements_file = os.path.join(d, "yum_requirements.txt")
-        if "docker" in os.environ.get("CI_RUNNER_TAGS", "").split(
-            ", "
-        ) and os.path.exists(yum_requirements_file):
+        if os.path.exists("/usr/bin/yum") and os.path.exists(
+            yum_requirements_file
+        ):
             logger.info(
                 "Installing packages from yum_requirements.txt file using yum"
             )