Update nightly.steps.yaml (#275)

Author: simonsarginson

.buildkite/nightly.steps.yaml

@@ -1,5 +1,5 @@
 ---
-ci_version: &ci_version "1.1"
+ci_version: &ci_version "1.2"
 
 steps:
   # New build pipeline
@@ -12,10 +12,10 @@ steps:
       message: "exampleproject-4.26 ${BUILDKITE_MESSAGE}"
       env: 
         BUILD_TYPE: "EXAMPLE"
-        GDK_BRANCH: "${GDK_BRANCH:-0.13.1-rc}" # NOTE: temp fix for new ci release interop issues
-        ENGINE_BRANCH: "${ENGINE_BRANCH:-4.26-SpatialOSUnrealGDK-0.13.1-rc}" # NOTE: temp fix for new ci release interop issues
+        GDK_BRANCH: "${GDK_BRANCH:-match_branch_name_pref::0.13.1-rc}"
+        ENGINE_BRANCH: "${ENGINE_BRANCH_426:-match_branch_name_pref_engine::4.26-SpatialOSUnrealGDK-0.13.1-rc}"
         ENGINE_MAJOR: "4.26"
-        PROJECT_BRANCH: "${BUILDKITE_BRANCH}"
+        PROJECT_BRANCH: "main_branch::${BUILDKITE_BRANCH}"
         USE_FASTBUILD: "True"
         IS_BUILDKITE_BUILD: "True"
         BUILD_ANDROID: "True"