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/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 2593681..b0c94a2 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -14,6 +14,10 @@
  * limitations under the License.
  */
 
+// TODO(b/129481165): remove the #pragma below and fix conversion issues
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wconversion"
+
 //#define LOG_NDEBUG 0
 #undef LOG_TAG
 #define LOG_TAG "Layer"
@@ -2304,3 +2308,6 @@
 #if defined(__gl2_h_)
 #error "don't include gl2/gl2.h in this file"
 #endif
+
+// TODO(b/129481165): remove the #pragma below and fix conversion issues
+#pragma clang diagnostic pop // ignored "-Wconversion"