DAP: system_as_root can't be true.

Test: builds
Change-Id: I3e47e9717c983703494abc8417526caf5955d2e4
Fixes: 124274480
diff --git a/core/config.mk b/core/config.mk
index ab0ec6d..8a22ce9 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -947,6 +947,10 @@
 endif
 
 ifeq ($(PRODUCT_USE_DYNAMIC_PARTITIONS),true)
+    ifeq ($(BOARD_BUILD_SYSTEM_ROOT_IMAGE),true)
+        $(error BOARD_BUILD_SYSTEM_ROOT_IMAGE cannot be true for devices with dynamic partitions)
+    endif
+
     requirements := \
         PRODUCT_USE_DYNAMIC_PARTITION_SIZE \
         PRODUCT_BUILD_SUPER_PARTITION \