Revert "llvm2alive: ignore llvm.fake.use()"

This reverts commit cdf00c6.

Author: jmciver

llvm_util/llvm2alive.cpp

@@ -1228,7 +1228,6 @@ class llvm2alive_ : public llvm::InstVisitor<llvm2alive_, unique_ptr<Instr>> {
     case llvm::Intrinsic::dbg_label:
     case llvm::Intrinsic::dbg_value:
     case llvm::Intrinsic::donothing:
-    case llvm::Intrinsic::fake_use:
     case llvm::Intrinsic::instrprof_increment:
     case llvm::Intrinsic::instrprof_increment_step:
     case llvm::Intrinsic::instrprof_value_profile: