Switch to clang-2658975.

Bug: http://b/27482631

This fixes an issue where krait compiles were not passing the proper
flags to the assembler when -no-integrated-as is used. This was
preventing ART from switching to clang in some cases.

(cherry picked from commit c503d8ef)

Change-Id: I4a0efb78f37fee73bf61841f0347328b8f61c192