fix the `was compiled for iOS Simulator, but linking for MacOSX` warning

We're seeing ...

```
ld: warning: ObjC object file
(/Users/fpotter/Library/Developer/Xcode/DerivedData/xctool-coaqfpnavanndzgumiqgxmfwpkjd/Build/Intermediates/otest-query.build/Debug/otest-query-ios.build/Objects-normal/i386/main.o)
was compiled for iOS Simulator, but linking for MacOSX
```

Where we used to pass `-miphoneos-version-min=7.0` in Xcode 4, we now
need to pass `-mios-simulator-version-min=7.0`.
adding a `-showTasks` option which logs info on all spawned tasks.

When `-showTasks` is passed, xctool will log a message for every NSTask
that is spawned.  Included in each message is short description of the
task's purpose and a command-line expression that can be copied/pasted
into bash to replicate that command.

The output looks like --
https://gist.github.com/fpotter/6981876

I've wanted this for a long time - it's going to be super helpful for
debugging problems.
fixing build break in OtestShimTests.m

LaunchTaskAndFeedOuputLinesToBlock requires a description argument now.
Building universal binaries
Fixed broken tests by forcing i386 when needed.
Fixing crash when option is missing an argument.
Merge pull request #197 from ryanrhee/reporterCrash

xctool crashes when setting `-reporter` without a next arg
Add support for -xcconfig option
Merge pull request #211 from ryanrhee/universal

Building universal binaries.
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.
workaround otest-shim-osx build hang when running Xcode 4.6 on 10.9