Update defines for libfuzzer builds

SkMalloc.h no longer #includes SkTypes.h which enabled the
SK_BUILD_FOR_FUZZER define. We should set that explicitly when
building our fuzz executables.

Change-Id: I4c6075a59e2cb9398d4d86ca442db7f04eaee972
Bug: oss-fuzz:54829
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/627756
Reviewed-by: Herb Derby <herb@google.com>
Owners-Override: Kevin Lubick <kjlubick@google.com>
2 files changed