Add recovery_available property to sysprop module

This is required for a sysprop module to be used by a module like the
init which is available both in core and recovery variants.

Test: m
Change-Id: I075428289f5bdce26e931ccf3262793ca6e4a0fd

sysprop/sysprop_library.go

@@ -44,6 +44,7 @@ type syspropLibraryProperties struct {
 type commonProperties struct {
 	Srcs               []string
 	Recovery           *bool
+	Recovery_available *bool
 	Vendor_available   *bool
 }