[asan] fix the ppc32 build (by Jakub Jelinek). Note that the LLVM build still builds only for 64-bit PowerPC, and not for 32-bit

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@199090 91177308-0d34-0410-b5e6-96231b3b80d8