Enable dyanmic image size for GSI

The original size number of GSI are fixed size. Change to give
size by the content with appending 64M bytes space.

Bug: 71970853
Test: `make systemimage` and check the out system.img
Change-Id: I345f5e22c2fee7b553fc3337e9bff0ba28f579e1
Merged-In: I345f5e22c2fee7b553fc3337e9bff0ba28f579e1
diff --git a/target/board/BoardConfigGsiCommon.mk b/target/board/BoardConfigGsiCommon.mk
index 24614de..e910514 100644
--- a/target/board/BoardConfigGsiCommon.mk
+++ b/target/board/BoardConfigGsiCommon.mk
@@ -10,6 +10,9 @@
 TARGET_USERIMAGES_SPARSE_EXT_DISABLED := true
 TARGET_USES_MKE2FS := true
 
+# Enable dyanmic system image size and reserved 64MB in it.
+BOARD_SYSTEMIMAGE_PARTITION_RESERVED_SIZE := 67108864
+
 # Android Verified Boot (AVB):
 #   Builds a special vbmeta.img that disables AVB verification.
 #   Otherwise, AVB will prevent the device from booting the generic system.img.