Fix "[compiler-rt] Refactor memintrinsic interceptors"

Fix the Fuchsia build. asan_interceptors_memintrinsics.cpp should not
include any interceptors on Fuchsia.

Reported-by: haowei
Link: https://logs.chromium.org/logs/fuchsia/buildbucket/cr-buildbucket/8779679021892159153/+/u/clang/build/stdout