Fix soong_config handling of CompressedApex

add_json_bool treats non-empty variable as "true" by default (which is
conventional in make). Fix treatment of PRODUCT_COMPRESSED_APEX to
support the value false.

Bug: 185537646
Test: OVERRIDE_PRODUCT_COMPRESSED_APEX=false m nothing && \
      grep CompressedApex out/soong/soong.variables
Change-Id: I0562a375be377ab67a1d064e37aff5970c4ac8dd
diff --git a/core/soong_config.mk b/core/soong_config.mk
index 17176df..ec67560 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -240,7 +240,7 @@
 
 $(call add_json_bool, InstallExtraFlattenedApexes, $(PRODUCT_INSTALL_EXTRA_FLATTENED_APEXES))
 
-$(call add_json_bool, CompressedApex, $(PRODUCT_COMPRESSED_APEX))
+$(call add_json_bool, CompressedApex, $(filter true,$(PRODUCT_COMPRESSED_APEX)))
 
 $(call add_json_bool, BoardUsesRecoveryAsBoot, $(filter true,$(BOARD_USES_RECOVERY_AS_BOOT)))