Revert "[vm] Move the interpreter under a flag."

This reverts commit 715ab7b30b.

Reason for revert: simarm and kernel precomp builds failing

Original change's description:
> [vm] Move the interpreter under a flag.
> 
> After this CL, the interpreter is included by default in the
> JIT VM under the flag --enable-interpreter.
> 
> Change-Id: I06458f20288d67981822788ee6e867c2127ebdd3
> Reviewed-on: https://dart-review.googlesource.com/71800
> Commit-Queue: Zach Anderson <zra@google.com>
> Reviewed-by: Alexander Markov <alexmarkov@google.com>
> Reviewed-by: Siva Annamalai <asiva@google.com>
> Reviewed-by: Régis Crelier <regis@google.com>
> Reviewed-by: Ryan Macnak <rmacnak@google.com>

TBR=rmacnak@google.com,alexmarkov@google.com,zra@google.com,asiva@google.com,regis@google.com

Change-Id: I3622f4dbe53288d07fc21b34ee5ff68f2682b36d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://dart-review.googlesource.com/74001
Reviewed-by: Zach Anderson <zra@google.com>
Commit-Queue: Zach Anderson <zra@google.com>

runtime/vm/compiler/assembler/disassembler_kbc.cc

@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if !defined(DART_PRECOMPILED_RUNTIME)
+#if defined(DART_USE_INTERPRETER)
 
 #include "vm/compiler/assembler/disassembler_kbc.h"
 
@@ -370,4 +370,4 @@ void KernelBytecodeDisassembler::Disassemble(const Function& function) {
 
 }  // namespace dart
 
-#endif  // !defined(DART_PRECOMPILED_RUNTIME)
+#endif  // defined(DART_USE_INTERPRETER)