On our Continuous Integration we use `sudo xcode-select` to switch Xcode versions frequently. Historically, we've had issues like this with `actool` during compilation:
```
Build failed: Command failed with exit code 255. stderr: When running <actool>. When building rule //libraries/foo/Foo#apple-asset-catalog,apple-test-bundle,dwarf,no-linkermap.
```
(the error comes from buck but the important part is that `actool` returns an exit code of 255).
We've fixed this in the past by killing `CoreSimulatorService` after switching Xcode. This is because for some reason, `actool` needs to communicate with the simulator (maybe over XPC?) and if you've recently switched Xcode versions, you might need to kill `CoreSimulatorService` before it will start working correctly.
However this year with Xcode 10, the issue has surfaced again.
The only fix I could find was converting the asset catalog that it was trying to compile to just normal PNG files. That restored stability to our CI, but we also were seeing this:
```
2018-09-24 17:36:13.343 ibtoold[26191:91510369] *** Assertion failure in -[IBMessageSendChannel sendMessage:returnValue:context:error:arguments:], /Library/Caches/com.apple.xbs/Sources/IDEInterfaceBuilder/IDEInterfaceBuilder-14313.18/Foundation/Utilities/IBMessageChannel.m:184
2018-09-24 17:36:13.444 ibtoold[26191:91510369] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Already shutdown'
*** First throw call stack:
(
0 CoreFoundation 0x00007fff4d7a82db __exceptionPreprocess + 171
1 libobjc.A.dylib 0x00007fff74945c76 objc_exception_throw + 48
2 CoreFoundation 0x00007fff4d7ae072 +[NSException raise:format:arguments:] + 98
3 Foundation 0x00007fff4f8d7340 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 193
4 IBFoundation 0x000000010dd31a72 -[IBMessageSendChannel sendMessage:returnValue:context:error:arguments:] + 2566
5 IDEInterfaceBuilderCocoaTouchIntegration 0x000000011b5c76d6 __159-[IBCocoaTouchImageCatalogToolProxy compileItemsWithCatalogRelativeIdentifierPaths:tagSolutionSpace:andStickerPacksWithCatalogRelativeIdentifierPaths:options:]_block_invoke + 132
6 IDEInterfaceBuilderKit 0x000000010cb2f528 -[IBAbstractPlatformToolProxy _ON_QUEUE_sendMessage:toChannelReturningError:during:] + 162
7 IDEInterfaceBuilderKit 0x000000010cb2f3a8 __74-[IBAbstractPlatformToolProxy sendMessage:toChannelReturningError:during:]_block_invoke + 38
8 libdispatch.dylib 0x00007fff75525db8 _dispatch_client_callout + 8
9 libdispatch.dylib 0x00007fff755391e1 _dispatch_queue_barrier_sync_invoke_and_complete + 60
10 DVTFoundation 0x000000010d59a3db DVTDispatchSync + 208
11 IDEInterfaceBuilderKit 0x000000010cb2f2cb -[IBAbstractPlatformToolProxy sendMessage:toChannelReturningError:during:] + 245
12 IDEInterfaceBuilderCocoaTouchIntegration 0x000000011b5c75f4 -[IBCocoaTouchImageCatalogToolProxy compileItemsWithCatalogRelativeIdentifierPaths:tagSolutionSpace:andStickerPacksWithCatalogRelativeIdentifierPaths:options:] + 220
13 IDEInterfaceBuilderCocoaTouchIntegration 0x000000011b5aeb3a -[IBICAbstractCocoaTouchPlatformAdapter compileCARItems:tagSolutionSpace:options:queue:completionHandler:] + 940
14 IDEInterfaceBuilderKit 0x000000010ca7dbad __84-[IBICAbstractPlatformAdapter compileSelectedItems:options:queue:completionHandler:]_block_invoke + 228
15 IDEInterfaceBuilderKit 0x000000010ca80fb4 __93-[IBICAbstractPlatformAdapter compileStandaloneCatalogItems:options:queue:completionHandler:]_block_invoke + 18
16 DVTFoundation 0x000000010d59a45e __DVTDispatchAsync_block_invoke + 97
17 libdispatch.dylib 0x00007fff7552d5fa _dispatch_call_block_and_release + 12
18 libdispatch.dylib 0x00007fff75525db8 _dispatch_client_callout + 8
19 libdispatch.dylib 0x00007fff75531395 _dispatch_main_queue_callback_4CF + 1148
20 CoreFoundation 0x00007fff4d760c19 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
21 CoreFoundation 0x00007fff4d722dfa __CFRunLoopRun + 2586
22 CoreFoundation 0x00007fff4d722153 CFRunLoopRunSpecific + 483
23 DVTFoundation 0x000000010d41fd3e -[NSRunLoop(DVTNSRunLoopAdditions) dvt_spinRunLoopInMode:whileBlockExecutesConcurrently:] + 457
24 DVTFoundation 0x000000010d4201e9 -[NSRunLoop(DVTNSRunLoopAdditions) dvt_spinRunLoopInMode:waitingForSemaphore:] + 128
25 ibtoold 0x000000010c7f7850 -[IBCLIImageCatalogToolPersona compileCatalogCollection:withPlatformAdapter:arguments:outputDictionary:] + 1622
26 ibtoold 0x000000010c7f9087 -[IBCLIImageCatalogToolPersona invokeArguments:outputDictionary:] + 1785
27 ibtoold 0x000000010c7f9631 -[IBCLIImageCatalogToolPersona runSingleInvocation:outputtingToFileHandle:andVerifyingEnvironment:] + 709
28 ibtoold 0x000000010c8070e7 IBCLIServerRunSingleInvocation + 520
29 ibtoold 0x000000010c80773e __IBCLIServerRunSingleInvocationWithIODirectedAtPipesAndUnlinkOnSuccess_block_invoke_2 + 34
30 ibtoold 0x000000010c80760c __IBCLIServerRunSingleInvocationWithIODirectedAtPipesAndUnlinkOnSuccess_block_invoke + 857
31 ibtoold 0x000000010c7f63f5 -[IBCLIErrorForwarder forwardErrorOutputToDescriptor:whileInvokingBlock:] + 110
32 ibtoold 0x000000010c806c9d IBCLIServerRunSingleInvocationWithIODirectedAtPipesAndUnlinkOnSuccess + 581
33 ibtoold 0x000000010c805a7d main + 2673
34 libdyld.dylib 0x00007fff7555f015 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
```
The "already shutdown" part makes me think that this is also simulator related.
Other than killing the `CoreSimulatorService` process, what else could I try that might help reset the simulator state here? Seeing these issues with Xcode 10 final release.
