SurfaceFlinger: Enable -WConversion in Android.bp

Enable global -WConversion in Android.bp and turn it off in
individual files. This is the first step to enable -WConversion
in SurfaceFlinger.

Test: boot
Bug: 129481165
Change-Id: Ia752df39ef380bde71705a32582d618242c466f7
diff --git a/services/surfaceflinger/tests/hwc2/Hwc2TestLayers.cpp b/services/surfaceflinger/tests/hwc2/Hwc2TestLayers.cpp
index 90127a1..b76ace8 100644
--- a/services/surfaceflinger/tests/hwc2/Hwc2TestLayers.cpp
+++ b/services/surfaceflinger/tests/hwc2/Hwc2TestLayers.cpp
@@ -13,6 +13,10 @@
  * limitations under the License.
  */
 
+// TODO(b/129481165): remove the #pragma below and fix conversion issues
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wconversion"
+
 #include <sstream>
 #include <gtest/gtest.h>
 
@@ -279,3 +283,6 @@
 
     return optimized;
 }
+
+// TODO(b/129481165): remove the #pragma below and fix conversion issues
+#pragma clang diagnostic pop // ignored "-Wconversion"