Make filesystem aware of coverage

filesystem should have coverage variants with coverage-enabled build.
Otherwise, it would fail to collect dependencies.

Bug: 273238141
Test: m nothing (soong tests)
Test: compare the artifacts
 $ SKIP_ABI_CHECKS=true SOONG_COLLECT_JAVA_DEPS=true EMMA_INSTRUMENT=true\
   EMMA_INSTRUMENT_FRAMEWORK=true CLANG_COVERAGE=true\
   NATIVE_COVERAGE_PATHS='*' m microdroid
 $ m microdroid
Change-Id: I792458ace00a63b4b5213898fd3209351a6e00be