Fix missing dependency in sepolicy mapping file rules

The system_ext_mapping_cil_$(ver) and product_mapping_cil_$(ver) rules
use build_sepolicy, but are missing a dependency on the tool.

Bug: 183865297
Test: forrest
Change-Id: Ic4e860ccf3e7a3cd06bc5c6fe947717fadb164f5
1 file changed