Workaround for b/30067360.

/proc/self/environ inaccessible in SurfaceFlinger
=> ASan fails to read ASAN_OPTIONS => alloc-dealloc-mismatch bug is not
suppressed and prevents the device from booting.

This is not perfect because, by enabling it in asan build only, the first several attempts to start
surfaceflinger fail while the /data partition is being encrypted. On the other hand, this does not affect
user builds, and device eventually gets up anyway.

Change-Id: I5803a1688c2218cd1c36e04473f588ca28f9689f