Implement path-based enabling of code coverage.

Native coverage is enabled by setting NATIVE_COVERAGE to true
and specifying a list of paths in the COVERAGE_PATHS
environment variable. Files are exported to a zip file in the
target out directory.

Change-Id: I66a2ddd88e849bec1cc0cdae1b51fe18a007e2c3
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 635dd55..5f7a705 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -191,7 +191,6 @@
 LOCAL_MODULE_UNSUPPORTED_HOST_CROSS_ARCH_WARN:=
 LOCAL_NO_FPIE :=
 LOCAL_CXX_STL := default
-LOCAL_NATIVE_COVERAGE :=
 LOCAL_DPI_VARIANTS:=
 LOCAL_DPI_FILE_STEM:=
 LOCAL_SANITIZE:=
@@ -236,6 +235,7 @@
 LOCAL_PREBUILT_JNI_LIBS_$(TARGET_ARCH):=
 LOCAL_STRIP_MODULE_$(TARGET_ARCH):=
 LOCAL_PACK_MODULE_RELOCATIONS_$(TARGET_ARCH):=
+LOCAL_GCNO_FILES:=
 ifdef TARGET_2ND_ARCH
 LOCAL_SRC_FILES_$(TARGET_2ND_ARCH):=
 LOCAL_SRC_FILES_EXCLUDE_$(TARGET_2ND_ARCH):=