[compiler-rt][Fuzzer] Use the new C++ ABI namespace CMake support
[compiler-rt][Fuzzer] Use the new C++ ABI namespace CMake support

libc++ now supports customizing the ABI namespace directly from the
CMake build so we no longer need to rely on custom CFLAGS.

Differential Revision: https://reviews.llvm.org/D53939

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@345765 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