Disable the object cache for reproducibility

It changes the memory allocation pattern based on the number / names? of the
cache files, making it very hard to get deterministic output from malloc.

docs/REFCOUNTING.md

@@ -33,7 +33,8 @@ If the program ends with a message such as "10 refs remaining!", try to bisect d
 
 If the assertion `assert(var->reftype != RefType::UNKNOWN)` fails in Rewriter::commitReturning(), this means that someone forgot to call `setType` on a refcounted RewriterVar.  Unfortunately, we don't have any tracking of where RewriterVars get created, so we will use GDB to help us.
 
-- Type `run` a few (~3) times to make sure that the program enters steady-state behavior (on-disk caches get filled).
+- First, turn off ENABLE_JIT_OBJECT_CACHE in options.cpp (maybe we should add a command line flag for this).
+-- You may need to type `run` a few (~3) times to make sure that the program enters steady-state behavior (on-disk caches get filled), though with the object cache off this shouldn't be necessary.
 - When the assertion hits, go up to the `commitReturning()` stack frame that contains the assertion.
 - Type `watch -l *(char**)&var->reftype`.  This adds a breakpoint that will get hit whenever the reftype field gets modified.  The `-l` flag tells gdb to evaluate the expression once and then watch the resulting address (rather than symbolically reevaluating it each time).  The `*(char**)&` part is a workaround since otherwise GDB will fail to reset the breakpoint when we do the next step.
 - Type `run` to restart the program.  You should see the breakpoint get hit.  We are only interested in the last time the breakpoint gets hit, so we need to do the following:

src/asm_writing/rewriter.cpp

@@ -1557,7 +1557,7 @@ bool Rewriter::finishAssembly(int continue_offset) {
 void Rewriter::commitReturning(RewriterVar* var) {
     STAT_TIMER(t0, "us_timer_rewriter", 10);
 
-    assert(var->reftype != RefType::UNKNOWN);
+    ASSERT(var->reftype != RefType::UNKNOWN, "%p", var);
 
     addAction([=]() {
         if (LOG_IC_ASSEMBLY) assembler->comment("commitReturning");

src/core/options.cpp

@@ -79,7 +79,7 @@ bool ENABLE_REOPT = 1 && _GLOBAL_ENABLE;
 bool ENABLE_PYSTON_PASSES = 0 && _GLOBAL_ENABLE;
 bool ENABLE_TYPE_FEEDBACK = 1 && _GLOBAL_ENABLE;
 bool ENABLE_RUNTIME_ICS = 1 && _GLOBAL_ENABLE;
-bool ENABLE_JIT_OBJECT_CACHE = 1 && _GLOBAL_ENABLE;
+bool ENABLE_JIT_OBJECT_CACHE = 0 && _GLOBAL_ENABLE;
 bool LAZY_SCOPING_ANALYSIS = 1;
 
 bool ENABLE_FRAME_INTROSPECTION = 1;