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/Credentials_test.cpp b/services/surfaceflinger/tests/Credentials_test.cpp
index f618873..a7c095d 100644
--- a/services/surfaceflinger/tests/Credentials_test.cpp
+++ b/services/surfaceflinger/tests/Credentials_test.cpp
@@ -31,6 +31,10 @@
  * Methods like EnableVsyncInjections and InjectVsync are not tested since they do not
  * return anything meaningful.
  */
+
+// TODO(b/129481165): remove the #pragma below and fix conversion issues
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wconversion"
 class CredentialsTest : public ::testing::Test {
 protected:
     void SetUp() override {
@@ -362,3 +366,6 @@
 }
 
 } // namespace android
+
+// TODO(b/129481165): remove the #pragma below and fix conversion issues
+#pragma clang diagnostic pop // ignored "-Wconversion"