[snapshot] do not embed string addresses in code.

src/mips/assembler-mips.cc

Index: src/mips/assembler-mips.cc
diff --git a/src/mips/assembler-mips.cc b/src/mips/assembler-mips.cc
index 11c8eaf20ccdf316dc94ed5b1fa3ecc86b66bbef..ab57e875489f3f3e3bbecc99eda51c4f35f14bff 100644
--- a/src/mips/assembler-mips.cc
+++ b/src/mips/assembler-mips.cc
@@ -1974,7 +1974,11 @@ void Assembler::stop(const char* msg, uint32_t code) {
   // The Simulator will handle the stop instruction and get the message address.
   // On MIPS stop() is just a special kind of break_().
   break_(code, true);
-  emit(reinterpret_cast<Instr>(msg));
+  // Do not embed the message string address! We used to do this, but that
+  // made snapshots created from position-independent executable builds
+  // non-deterministic.
+  // TODO(yangguo): remove this field entirely.
+  nop();
 #endif
 }