Mark bullhead as containing duplicate build rules

Bug: 77611511
Test: with https://android-review.googlesource.com/c/platform/build/soong/+/709015
Change-Id: I49a08316798a23ad13df129f53f519827e779471
diff --git a/BoardConfig.mk b/BoardConfig.mk
index b256fa0..0e6e0fb 100644
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -14,6 +14,8 @@
 # limitations under the License.
 #
 
+BUILD_BROKEN_DUP_RULES := true
+
 TARGET_ARCH := arm64
 TARGET_ARCH_VARIANT := armv8-a
 TARGET_CPU_ABI := arm64-v8a