Refactor LOCAL_INIT_RC

We supported de-duplicating LOCAL_INIT_RC across multiple architecture
variants in a single module definition, but that didn't work if the
module was defined with two different BUILD_PREBUILT definitions. That's
how we're exporting modules from Soong to Make.

Change-Id: Ifc93b15ef78ea3d8e78005d428a3ec57d7e414e8
diff --git a/core/definitions.mk b/core/definitions.mk
index 53a6fcd..8ef67f1 100644
--- a/core/definitions.mk
+++ b/core/definitions.mk
@@ -95,6 +95,9 @@
 HOST_DISPLAY := host
 HOST_CROSS_DISPLAY := host cross
 
+# All installed initrc files
+ALL_INIT_RC_INSTALLED_PAIRS :=
+
 ###########################################################
 ## Debugging; prints a variable list to stdout
 ###########################################################