Switch from clang 3.6 to new clang repository (with 3.8).

Bug: 23396112

Switch from "-fsanitize-undefined-trap-on-error" to
"-fsanitize-trap=all". The former ends up accidentally leaving
unresolved calls to __ubsan* helper functions in the object file with
clang 3.8. The latter is used when we don't include address sanitizer,
and replaces any misbehavior with a direct call to abort().

Change-Id: I8a67461b45f5f1dd9f2d179b6b64a4ca905e999f