Define BOARD_API_LEVEL_PROP_OVERRIDE for GRF prop

When BOARD_API_LEVEL_PROP_OVERRIDE is set, ro.board.api_level is set
to this value. The original BOARD_API_LEVEL is still used for the
vendor API surface.

Bug: 374333106
Test: set BOARD_API_LEVEL_PROP_OVERRIDE and see ro.board.api_level
Change-Id: I842e93c4c9c6aeaf3acb9a7b670adce0d9e96ba7
diff --git a/core/soong_config.mk b/core/soong_config.mk
index a511d5c..a5cbfc9 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -150,6 +150,7 @@
 $(call add_json_str,  BtConfigIncludeDir,                $(BOARD_BLUETOOTH_BDROID_BUILDCFG_INCLUDE_DIR))
 $(call add_json_list, DeviceKernelHeaders,               $(TARGET_DEVICE_KERNEL_HEADERS) $(TARGET_BOARD_KERNEL_HEADERS) $(TARGET_PRODUCT_KERNEL_HEADERS))
 $(call add_json_str,  VendorApiLevel,                    $(BOARD_API_LEVEL))
+$(call add_json_str,  VendorApiLevelPropOverride,        $(BOARD_API_LEVEL_PROP_OVERRIDE))
 $(call add_json_list, ExtraVndkVersions,                 $(PRODUCT_EXTRA_VNDK_VERSIONS))
 $(call add_json_list, DeviceSystemSdkVersions,           $(BOARD_SYSTEMSDK_VERSIONS))
 $(call add_json_list, Platform_systemsdk_versions,       $(PLATFORM_SYSTEMSDK_VERSIONS))