[HWASan] Initalize shadow earler.
[HWASan] Initalize shadow earler.

Summary:
Initialize shadow memory before calling more libc functions to allow
for HWASan-instrumented libc.

Reviewers: eugenis

Subscribers: kubamracek, delcypher, #sanitizers, llvm-commits

Differential Revision: https://reviews.llvm.org/D48551

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@335502 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt