[sanitizer] Allow Fuchsia to use getauxval
Summary:
Fuchsia has `getauxval` (https://fuchsia.googlesource.com/zircon/+/master/third_party/ulib/musl/include/sys/auxv.h,
https://fuchsia.googlesource.com/zircon/+/master/third_party/ulib/musl/src/misc/getauxval.c)
so set SANITIZER_USE_GETAUXVAL to 1 for this platform.
Reviewers: alekseyshl, flowerhack
Reviewed By: flowerhack
Subscribers: srhines, kubamracek, #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D42315
llvm-svn: 323002