sm8450-common: Add exclusion for vendor ELF prebuilts

 - ELF prebuilts were banned in PRODUCT_COPY_FILES starting May 11.
 - Adding BUILD_BROKEN_ELF_PREBUILT_PRODUCT_COPY_FILES := true to
BoardConfig.mk temoporarily.
 - See b/156534160 for long-term fix which should override this change.

Test: Build
Bug: 156534160
Change-Id: I7d80798d3b2d3818bc835fcede21de2e7ab04735

BoardConfigCommon.mk

@@ -10,6 +10,7 @@ include vendor/xiaomi/sm8450-common/BoardConfigVendor.mk
 COMMON_PATH := device/xiaomi/sm8450-common
 
 BUILD_BROKEN_DUP_RULES := true
+BUILD_BROKEN_ELF_PREBUILT_PRODUCT_COPY_FILES := true
 
 # A/B
 AB_OTA_UPDATER := true