Skip installer build on non-release branches

appveyor.yml

@@ -37,9 +37,14 @@ install:
 build_script:
   - CD %APPVEYOR_BUILD_FOLDER%
   - IF [%TASK%]==[installer] (
-      SET BUILD_ARG=--create-windows-installer
+      IF [%APPVEYOR_REPO_BRANCH:~-9%]==[-releases] (
+        SET BUILD_ARG=--create-windows-installer
+      ) ELSE (
+        ECHO "Skipping installer build on non-release branch"
+      )
     ) ELSE (
-      SET BUILD_ARG=
+      SET BUILD_ARG= &&
+      ECHO "Skipping installer build on non-installer build matrix row"
     )
   - script\build.cmd --code-sign --compress-artifacts %BUILD_ARG%