Header Finding Issue

Hey all, thanks for making such a neat tool.

It's possible I'm missing something silly here, but I'm having issues with includes in what seems like it should be a relatively straightforward case.

I'm trying to use the [GBDeviceInfo](https://github.com/lmirosevic/GBDeviceInfo) /Core podspec.

`bazel build @GBDeviceInfo//:Core --keep_going` fails because it can't find the pod's headers
```
bazel-out/apl-darwin_x86_64-fastbuild/bin/external/GBDeviceInfo/GBDeviceInfo_module_map/../../../../../../external/GBDeviceInfo/GBDeviceInfo/GBDeviceInfo.h:33:9: fatal error: 'GBDeviceInfo_OSX.h' file not found
#import "GBDeviceInfo_OSX.h"
^~~~~~~~~~~~~~~~~~~~
external/GBDeviceInfo/GBDeviceInfo/ GBDeviceInfo_iOS.m:20:9: fatal error: could not build module 'GBDeviceInfo'
#import "GBDeviceInfo_iOS.h"
~~~~~~~^~~~~~~~~~~~~~~~~~~~
```

I see two issues there. First, that it's not finding the GBDeviceInfo_OSX.h header--which should be in there. And second it seems strange that it's trying to compile GBDeviceInfo_iOS.m on mac, when that source is marked as iOS-only in the podspec.

Is there something straightforward I'm missing here? It feels like this should be mostly parallel to PINOperation, but that example works fine.

Thanks so much,
Chris

P.S. For reference, my WORKSPACE just has the basics added. The only change from your example is moving to the latest release of this repo (PodToBUILD):
```
http_archive(
name = "rules_pods",
urls = ["https://github.com/pinterest/PodToBUILD/releases/download/0.25.2-8a5efa0/PodToBUILD.zip"],
)

load("@rules_pods//BazelExtensions:workspace.bzl", "new_pod_repository")

new_pod_repository(
name = "GBDeviceInfo",
url = "https://github.com/lmirosevic/GBDeviceInfo/archive/6.3.0.zip",
)
```