Export build flags to soong.

This exports a map of build flags used in this release config to Soong.

Bug: b/302514918
Test: manual
Change-Id: Ia93195f09dee4945f07326eb7a5973c2ce2e025b
diff --git a/core/soong_config.mk b/core/soong_config.mk
index be6a795..e39f2fa 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -169,6 +169,11 @@
 $(call add_json_bool, VndkUseCoreVariant,                $(TARGET_VNDK_USE_CORE_VARIANT))
 $(call add_json_bool, VndkSnapshotBuildArtifacts,        $(VNDK_SNAPSHOT_BUILD_ARTIFACTS))
 
+$(call add_json_map,  BuildFlags)
+$(foreach flag,$(_ALL_RELEASE_FLAGS),\
+  $(call add_json_str,$(flag),$(_ALL_RELEASE_FLAGS.$(flag).VALUE)))
+$(call end_json_map)
+
 $(call add_json_bool, DirectedVendorSnapshot,            $(DIRECTED_VENDOR_SNAPSHOT))
 $(call add_json_map,  VendorSnapshotModules)
 $(foreach module,$(VENDOR_SNAPSHOT_MODULES),\