don't set IPHONE_SIMULATOR_VERSIONS when running otest-query

There's no need.

I did a grep over all the iOS frameworks ...

```
grep -R IPHONE_SIMULATOR_VERSIONS
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator7.0.sdk
```

... and found that it's only used by libSystem.dylib, and then, only as
an extra blob of text that is appended to crash reports.  We definitely
don't need this for the purposes of otest-query.
Set IPHONE_SIMULATOR_VERSIONS according to the SDK version

Fixes issue #157
fix test breaking when calling GetSDKVersionString on uninstalled SDK

We were hitting asserts in GetSDKVersionString whenever the specified
SDK version didn't exist.

This would happen in a couple of our tests which were written against
old versions of the iOS SDK (like iphonesimulator5.0), which aren't
commonly installed.