graphics: add gralloc tests to VTS

Test: vts-tradefed run vts -m HalGraphicsAllocatorHidlTargetTest
Test: vts-tradefed run vts -m HalGraphicsMapperHidlTargetTest
Change-Id: I35e03b42e693da1bd3cfc6beac2a64771e0b8ed9
diff --git a/graphics/mapper/2.0/vts/functional/Android.bp b/graphics/mapper/2.0/vts/functional/Android.bp
index e324322..53e6d16 100644
--- a/graphics/mapper/2.0/vts/functional/Android.bp
+++ b/graphics/mapper/2.0/vts/functional/Android.bp
@@ -33,7 +33,11 @@
     ],
     static_libs: ["libgtest"],
     cflags: [
+        "--coverage",
         "-O0",
         "-g",
     ],
+    ldflags: [
+        "--coverage",
+    ],
 }