[osx] unbreak EmergencyMallocNoHook test

OSX's malloc zones stuff is essentially incompatible with emergency
malloc. In order to handle it, our unit tests use tc_free directly in
order to free memory allocated by emergency malloc. So lets keep doing
it for our newer code that exercises calloc/free pair as well.

src/libc_override_osx.h

@@ -108,6 +108,9 @@ extern "C" {
 // We need to provide wrappers around all the libc functions.
 namespace {
 size_t mz_size(malloc_zone_t* zone, const void* ptr) {
+  // Note, this does not work for emergency malloc's memory. And in
+  // principle OSX doesn't need or use it. But by default we enable
+  // it, so that our unit test coverage is wider.
   if (MallocExtension::instance()->GetOwnership(ptr) != MallocExtension::kOwned)
     return 0;  // malloc_zone semantics: return 0 if we don't own the memory
 

src/tests/tcmalloc_unittest.cc

@@ -1609,7 +1609,7 @@ TEST(TCMallocTest, EmergencyMallocNoHook) {
   portal->WithEmergencyMallocEnabled([&] () {
     p2 = noopt(malloc)(32);
     for (int i = 11; i < 999; i++) {
-      free(p3);
+      tc_free(p3);
       p3 = tc_calloc(1, i);
     }
     p4 = tc_calloc(4096, 1024);