[msbuild] Always codesign the framework directory, not what's inside (x…

…amarin#10309)

**Example #1.** Signing a framework binary is the **same** thing as
signing the framework directory.

```
$ codesign -v --force --timestamp=none --sign - bin/iPhone/Release/xcf_ios.app//Frameworks/lame.framework/lame
bin/iPhone/Release/xcf_ios.app//Frameworks/lame.framework/lame: replacing existing signature
bin/iPhone/Release/xcf_ios.app//Frameworks/lame.framework/lame: signed bundle with Mach-O thin (arm64) [io.sourceforge.lame]

$ codesign -v --force --timestamp=none --sign - bin/iPhone/Release/xcf_ios.app//Frameworks/lame.framework
bin/iPhone/Release/xcf_ios.app//Frameworks/lame.framework: replacing existing signature
bin/iPhone/Release/xcf_ios.app//Frameworks/lame.framework: signed bundle with Mach-O thin (arm64) [io.sourceforge.lame]
```

Nice right ? Pretty much until...

**Example #2.** Signing a framework binary is **NOT** the **same** thing
as signing the framework directory.

```
$ codesign -v --force --timestamp=none --sign - bin/iPhone/Release/xcf_ios.app//Frameworks/flac.framework/flac
bin/iPhone/Release/xcf_ios.app//Frameworks/flac.framework/flac: replacing existing signature
bin/iPhone/Release/xcf_ios.app//Frameworks/flac.framework/flac: signed Mach-O thin (arm64) [flac-55554944583d2f02282c33d8bfed082daa857e30]

$ codesign -v --force --timestamp=none --sign - bin/iPhone/Release/xcf_ios.app//Frameworks/flac.framework
bin/iPhone/Release/xcf_ios.app//Frameworks/flac.framework: replacing existing signature
bin/iPhone/Release/xcf_ios.app//Frameworks/flac.framework: signed bundle with Mach-O thin (arm64) [org.xiph.flac]
```

In this case signing the binary `flac` does not produce the
`_CodeSignature` directory and fails our msbuild Codesign task

The fix is to detect if we're signing a framework like `A.framework/A`
and change this to sign `A.framework` as this will always work.

msbuild/Xamarin.MacDev.Tasks.Core/Tasks/CodesignTaskBase.cs

@@ -140,7 +140,16 @@ IList<string> GenerateCommandLineArguments (ITaskItem item)
 			if (!string.IsNullOrEmpty (ExtraArgs))
 				args.Add (ExtraArgs);
 
-			args.Add (Path.GetFullPath (item.ItemSpec));
+			// signing a framework and a file inside a framework is not *always* identical
+			// on macOS apps {item.ItemSpec} can be a symlink to `Versions/Current/{item.ItemSpec}`
+			// and `Current` also a symlink to `A`... and `_CodeSignature` will be found there
+			var path = PathUtils.ResolveSymbolicLinks (item.ItemSpec);
+			var parent = Path.GetDirectoryName (path);
+
+			// so do not don't sign `A.framework/A`, sign `A.framework` which will always sign the *bundle*
+			if ((Path.GetExtension (parent) == ".framework") && (Path.GetFileName (path) == Path.GetFileNameWithoutExtension (parent)))
+				path = parent;
+			args.Add (Path.GetFullPath (path));
 
 			return args;
 		}
@@ -230,14 +239,6 @@ IEnumerable<ITaskItem> GetCodesignedFiles (ITaskItem item)
 				}
 			} else if (File.Exists (item.ItemSpec)) {
 				codesignedFiles.Add (item);
-
-				// on macOS apps {item.ItemSpec} can be a symlink to `Versions/Current/{item.ItemSpec}`
-				// and `Current` also a symlink to `A`... and `_CodeSignature` will be found there
-				var path = PathUtils.ResolveSymbolicLinks (item.ItemSpec);
-				var dirName = Path.GetDirectoryName (path);
-
-				if (Path.GetExtension (dirName) == ".framework")
-					codesignedFiles.AddRange (Directory.EnumerateFiles (Path.Combine (dirName, CodeSignatureDirName)).Select (x => new TaskItem (x)));
 			}
 
 			return codesignedFiles;