gsi_skip_mount.cfg skips system sub-mountpoints

Bug: 184132970
Test: GSI Boot test
Change-Id: I6cb6735d41b6dc6c19a27d730226b200d362bc1d
diff --git a/target/product/gsi/gsi_skip_mount.cfg b/target/product/gsi/gsi_skip_mount.cfg
index ad3c7d9..28f4349 100644
--- a/target/product/gsi/gsi_skip_mount.cfg
+++ b/target/product/gsi/gsi_skip_mount.cfg
@@ -1,3 +1,9 @@
+# Skip "system" mountpoints.
 /oem
 /product
 /system_ext
+# Skip sub-mountpoints of system mountpoints.
+/oem/*
+/product/*
+/system_ext/*
+/system/*