In single_threaded mode MiniRacer will behave far more reasonably if platform
is initialized in the master process.
Sadly this is only a partial solution since we will hang at:
```
#0 0x00007fe6f037e34d in pthread_cond_broadcast@@GLIBC_2.3.2 () from /usr/lib/libpthread.so.0
#1 0x00007fe6ebc15c05 in v8::platform::DelayedTaskQueue::Terminate() ()
from /home/sam/Source/mini_racer/lib/mini_racer_extension.so
#2 0x00007fe6ebc14dfd in v8::platform::DefaultWorkerThreadsTaskRunner::Terminate() ()
from /home/sam/Source/mini_racer/lib/mini_racer_extension.so
#3 0x00007fe6ebc13bd6 in v8::platform::DefaultPlatform::~DefaultPlatform() ()
from /home/sam/Source/mini_racer/lib/mini_racer_extension.so
#4 0x00007fe6ebc13cde in v8::platform::DefaultPlatform::~DefaultPlatform() ()
from /home/sam/Source/mini_racer/lib/mini_racer_extension.so
#5 0x00007fe6effb0db7 in __run_exit_handlers () from /usr/lib/libc.so.6
```
Likely some more v8 changes are needed to mitigate the heavily forked use
case.
Brandon Fish