Determine build_ota_package based on recovery.fstab install location

recovery_fstab can be installed even if is not defined via
TARGET_RECOVERY_FSTAB_GENRULE. This change modifies the conditional in
determining build_ota_package to take such scenarios into account.

Test: m otapackage
Change-Id: Ia859b63aab902920ef7f44e4d8e09537e0e9dfad
diff --git a/core/Makefile b/core/Makefile
index 5d82c21..8973182 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -5649,7 +5649,7 @@
         build_ota_package := false
       endif
     endif # INSTALLED_BOOTIMAGE_TARGET == ""
-    ifeq ($(recovery_fstab),)
+    ifeq ($(filter $(TARGET_RECOVERY_ROOT_OUT)/system/etc/recovery.fstab,$(INTERNAL_RECOVERYIMAGE_FILES)),)
       build_ota_package := false
     endif
   endif # PRODUCT_BUILD_GENERIC_OTA_PACKAGE