Disable warnings triggered in Clang r271374

http://b/28149048
http://b/29823425

Disable -Wconstant-conversion and -Wundefined-var-template.  The second
bug above tracks that these warnings get reenabled.

Test: Tested build, boot and common usage for Arm, Arm64, x86, x86_64,
Mips images in AOSP and internal branch.

Change-Id: Iea20cf6b5dbec3247b55cf8130f88202e786e367
diff --git a/build/Android.common_build.mk b/build/Android.common_build.mk
index bd13d16..a679ac2 100644
--- a/build/Android.common_build.mk
+++ b/build/Android.common_build.mk
@@ -158,6 +158,10 @@
 # Enable warning for unreachable break & return.
 art_clang_cflags += -Wunreachable-code-break -Wunreachable-code-return
 
+# Bug: http://b/29823425  Disable -Wconstant-conversion and
+# -Wundefined-var-template for Clang update to r271374
+art_clang_cflags += -Wno-constant-conversion -Wno-undefined-var-template
+
 # Enable missing-noreturn only on non-Mac. As lots of things are not implemented for Apple, it's
 # a pain.
 ifneq ($(HOST_OS),darwin)