Only target UnityFramework when integrating Cocoapods.

Unity 2019.3 split iOS builds into a launcher target called
Unity-iPhone and a framework called UnityFramework.

When support for this was added in
I2236b4cfa08f64feb6e6a7957d71987cdacaa6a9 and
I1f236eaeca28bcfd051cc6ea317e5a888efe231e
the iOS resolver was changed to add Cocoapods to both targets.
However, this can result in build errors where symbols are
duplicated from Cocoapods being included in both targets as
UnityFramework is eventually included by Unity-iPhone.

This changes the resolver to only add to the UnityFramework
target when multiple Xcode targets are exported by Unity.

Fixes googlesamples#282
Bug: 136038764
Bug: 141944403
Change-Id: Ie26cc8ee8d503ddcb5a6fc779f8f9e814355c4cb

Author: Stewart Miles

source/IOSResolver/src/IOSResolver.cs

@@ -1617,7 +1617,7 @@ public static IEnumerable<string> XcodeTargetNames {
         get {
             // Return hard coded names in the UnityEditor.iOS.Xcode.PBXProject DLL.
             return MultipleXcodeTargetsSupported ?
-                new List<string>() { "Unity-iPhone", "UnityFramework" } :
+                new List<string>() { "UnityFramework" } :
                 new List<string>() { InitializeTargetName() };
         }
     }
@@ -1635,7 +1635,7 @@ public static IEnumerable<string> GetXcodeTargetGuids(object xcodeProject) {
             // NOTE: The test target is not exposed.
             try {
                 foreach (var guidMethod in
-                         new[] { "GetUnityMainTargetGuid", "GetUnityFrameworkTargetGuid" }) {
+                         new[] { "GetUnityFrameworkTargetGuid" }) {
                     targets.Add((string)VersionHandler.InvokeInstanceMethod(project, guidMethod,
                                                                             null));
                 }