Fix initialization-order bug in llvm::Support::TimeValue. TimeValue::now() is explicitly called during module initialization of lib/Support/Process.cpp. It reads the field of global object PosixZeroTime, which is not guaranteed to be initialized at this point. Found by AddressSanitizer with -fsanitize=init-order option.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175509 91177308-0d34-0410-b5e6-96231b3b80d8