We use `-Werror` in the Android test builds to make sure there are no warnings that we care about (e.g. unused flags). However, the NDK r13 tools produce a warning about their own builtins: ``` <built-in>: In function 'float abs(float)': <built-in>: warning: conflicts with previous declaration here [-Wattributes] ``` Suppress this warning so that we can continue using `-Werror` but tolerate these warnings.