Add an misc_info.txt entry to customize VABC compression

Products can define PRODUCT_VIRTUAL_AB_COMPRESSION_METHOD
to specify the compression algorithm they prefer, or "none"
for no compression at all.

Test: th
Change-Id: I4fa27bd2c87b8f46c51023168d079e9b47ce2924
diff --git a/core/Makefile b/core/Makefile
index b9103ab..9314b94 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -5170,6 +5170,11 @@
     echo "virtual_ab=true" >> $(1))
   $(if $(filter true,$(PRODUCT_VIRTUAL_AB_COMPRESSION)), \
     echo "virtual_ab_compression=true" >> $(1))
+# This value controls the compression algorithm used for VABC
+# valid options are defined in system/core/fs_mgr/libsnapshot/cow_writer.cpp
+# e.g. "none", "gz", "brotli"
+  $(if $(PRODUCT_VIRTUAL_AB_COMPRESSION_METHOD), \
+    echo "virtual_ab_compression_method=$(PRODUCT_VIRTUAL_AB_COMPRESSION_METHOD)" >> $(1))
   $(if $(filter true,$(PRODUCT_VIRTUAL_AB_OTA_RETROFIT)), \
     echo "virtual_ab_retrofit=true" >> $(1))
 endef