Increase system image size

More things got put into the default runtime apex, we need a bigger
system partition.

Bug: 133173474
Test: lunch qemu_trusty_arm64-userdebug; make; run trusty test suite
diff --git a/BoardConfig.mk b/BoardConfig.mk
index f813be4..d39346e 100644
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -39,7 +39,7 @@
 QEMU_CUSTOMIZATIONS := true
 
 TARGET_USERIMAGES_USE_EXT4 := true
-BOARD_SYSTEMIMAGE_PARTITION_SIZE := 268435456 # 256M
+BOARD_SYSTEMIMAGE_PARTITION_SIZE := 536870912 # 512M
 BOARD_USERDATAIMAGE_PARTITION_SIZE := 67108864 # 64M
 TARGET_COPY_OUT_VENDOR := vendor
 # ~100 MB vendor image. Please adjust system image / vendor image sizes