Build native coverage variant of APEXes when needed

When the native coverage is enabled, APEXes (and files there) are built
for native coverage as well.

Bug: 138952487
Test: make -j NATIVE_COVERAGE=true COVERAGE_PATHS='*' com.android.resolv
find out -name "*.gcno" | grep DnsResolver shows files

Test: libnetd_resolv.zip is found under
$(TARGET_OUT)/apex/com.android.resolv/lib directory

Change-Id: I97bcee9bf8ffc0dc71453abbdb613ed56ea2cdb4