Ignore a warning we trip because clang is too old.

The sv ud literal was added to C++17 for creating string_views, but
the Clang we have doesn't know that so it warns about using a
reserved ud literal name. Disable the warning since it's not
important here anyway.

Test: ./run_tests.py
Bug: http://b/34740564
Change-Id: I7b59a4b63969252d4df012df3c11d7638cbfa5a0

buildcmds/Android.mk

@@ -31,6 +31,7 @@ LOCAL_CPPFLAGS := \
     -UNDEBUG \
     -w \
     -Wno-error=non-virtual-dtor \
+    -Wno-reserved-user-defined-literal \
 
 # Optimization is causing relocation for nothrow new to be thrown away.
 # http://llvm.org/bugs/show_bug.cgi?id=21421