Prefer mavenCentral for plugin artifact download

mavenCentral has some artifacts signed whereas the same ones
on gradlePluginPortal are not signed. Add the order to prefer
fetching from mavenCentral first.

Test: GRADLE_USER_HOME=../../out11 ./gradlew tasks -> now passes
Change-Id: I5564d63ecfa3f9e25064ac7499646314255c1621
diff --git a/settings.gradle.kts b/settings.gradle.kts
new file mode 100644
index 0000000..be5fbb7
--- /dev/null
+++ b/settings.gradle.kts
@@ -0,0 +1,9 @@
+pluginManagement {
+    repositories {
+        // Prefer mavenCentral as that has signed artifacts
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
+
+include(":stub-annotations")
\ No newline at end of file