Native Coverage support in Soong (gcov)

This is configured the same as make -- a global NATIVE_COVERAGE=true
flag to allow native coverage, then COVERAGE_PATHS=path1,path2,... to
turn it on for certain paths.

There are .gcnodir files exported to Make and saved in $OUT/coverage/...
files which are `ar` archives containing all of the compiler-produced
.gcno files for a particular executable / shared library.

Unlike the Make implementation, this only passes links the helper
library (automatically through --coverage) when one of the object files
or static libraries being used actually has coverage enabled.

Host support is currently disabled, since we set -nodefaultlibs, which
prevents libclang_rt.profile-*.a from being picked up automatically.

Bug: 32749731
Test: NATIVE_COVERAGE=true COVERAGE_PATHS=system/core/libcutils m -j libbacktrace libutils tombstoned
      $OUT/coverage/system/lib*/libcutils.gcnodir looks correct (self)
      $OUT/coverage/system/lib*/libbacktrace.gcnodir looks correct (static)
      $OUT/coverage/system/lib*/libutils.gcnodir doesn't exist (shared)
      $OUT/coverage/system/bin/tombstoned.gcnodir looks correct (executable)
Test: NATIVE_COVERAGE=true COVERAGE_PATHS=external/libcxxabi m -j libc++
      Confirm that $OUT/coverage/system/lib*/libc++.gcnodir looks correct (whole_static_libs)
Change-Id: I48aaa0ba8d76e50e9c2d1151421c0c6dc8ed79a9
diff --git a/cc/library.go b/cc/library.go
index 8474f96..efaf440 100644
--- a/cc/library.go
+++ b/cc/library.go
@@ -199,6 +199,9 @@
 
 	sanitize *sanitize
 
+	// Output archive of gcno coverage information files
+	coverageOutputFile android.OptionalPath
+
 	// Decorated interafaces
 	*baseCompiler
 	*baseLinker
@@ -393,12 +396,12 @@
 
 	outputFile := android.PathForModuleOut(ctx,
 		ctx.ModuleName()+library.Properties.VariantName+staticLibraryExtension)
+	builderFlags := flagsToBuilderFlags(flags)
 
-	if ctx.Darwin() {
-		TransformDarwinObjToStaticLib(ctx, library.objects.objFiles, flagsToBuilderFlags(flags), outputFile, objs.tidyFiles)
-	} else {
-		TransformObjToStaticLib(ctx, library.objects.objFiles, flagsToBuilderFlags(flags), outputFile, objs.tidyFiles)
-	}
+	TransformObjToStaticLib(ctx, library.objects.objFiles, builderFlags, outputFile, objs.tidyFiles)
+
+	library.coverageOutputFile = TransformCoverageFilesToLib(ctx, library.objects, builderFlags,
+		ctx.ModuleName()+library.Properties.VariantName)
 
 	library.wholeStaticMissingDeps = ctx.GetMissingDependencies()
 
@@ -506,6 +509,10 @@
 		deps.StaticLibs, deps.LateStaticLibs, deps.WholeStaticLibs,
 		linkerDeps, deps.CrtBegin, deps.CrtEnd, false, builderFlags, outputFile)
 
+	objs.coverageFiles = append(objs.coverageFiles, deps.StaticLibObjs.coverageFiles...)
+	objs.coverageFiles = append(objs.coverageFiles, deps.WholeStaticLibObjs.coverageFiles...)
+	library.coverageOutputFile = TransformCoverageFilesToLib(ctx, objs, builderFlags, library.getLibName(ctx))
+
 	return ret
 }