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

filesystem/filesystem.go

@@ -22,6 +22,7 @@ import (
 	"strings"
 
 	"android/soong/android"
+	"android/soong/cc"
 
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
@@ -498,3 +499,11 @@ func sha1sum(values []string) string {
 	}
 	return fmt.Sprintf("%x", h.Sum(nil))
 }
+
+// Base cc.UseCoverage
+
+var _ cc.UseCoverage = (*filesystem)(nil)
+
+func (*filesystem) IsNativeCoverageNeeded(ctx android.BaseModuleContext) bool {
+	return ctx.Device() && ctx.DeviceConfig().NativeCoverageEnabled()
+}