FinderInfo metadata can make builds unsignable

It's possible to add BundleResource files to a project that contain metadata (xattrs) that later will cause a build to be unsignable with this error:

```
Tool /usr/bin/codesign execution started with arguments: -v --force --sign 8300ADA869DB5BDFFBE11F6BE2AD4A6616EDFE8C --entitlements /Users/fak/Dropbox/Projects/Circuit2/Circuit/obj/iPhone/Release/Entitlements.xcent /Users/fak/Dropbox/Projects/Circuit2/Circuit/bin/iPhone/Release/Circuit2.app
bin/iPhone/Release/Circuit2.app : error : /Users/fak/Dropbox/Projects/Circuit2/Circuit/bin/iPhone/Release/Circuit2.app: resource fork, Finder information, or similar detritus not allowed
```

The culprit is `com.apple.FinderInfo` and is clearable using instructions here: https://stackoverflow.com/questions/39652867/code-sign-error-in-macos-high-sierra-xcode-resource-fork-finder-information

### Steps to Reproduce

You need a file with `com.apple.FinderInfo`, here's one silly way to create one:

1. Open a JPEG in Preview.app
2. Duplicate it (Shift-Cmd-S)
3. Resize it (Tools, Adjust Size...)
4. Save it

### Expected Behavior

It would be nice if the tooling cleared the metadata for me.

Alternatively, just giving a better error and locating the bad files is OK too.

### Actual Behavior

Error

### Environment

```
=== Visual Studio Enterprise 2017 for Mac ===

Version 7.7 (build 1868)
Installation UUID: 4ba352e1-73e8-4dab-a9db-28012ca05af8
GTK+ 2.24.23 (Raleigh theme)
Xamarin.Mac 4.4.1.178 (master / eeaeb7e6)

Package version: 516000221

=== Mono Framework MDK ===

Runtime:
Mono 5.16.0.221 (2018-06/b63e5378e38) (64-bit)
Package version: 516000221

=== NuGet ===

Version: 4.7.0.5148

=== .NET Core ===

Runtime: /usr/local/share/dotnet/dotnet
Runtime Versions:
2.1.2
2.1.0-preview2-26406-04
2.0.3
SDK: /usr/local/share/dotnet/sdk/2.1.302/Sdks
SDK Versions:
2.1.302
2.1.300-preview2-008530
2.0.3
MSBuild SDKs: /Library/Frameworks/Mono.framework/Versions/5.16.0/lib/mono/msbuild/15.0/bin/Sdks

=== Xamarin.Profiler ===

Version: 1.6.4
Location: /Applications/Xamarin Profiler.app/Contents/MacOS/Xamarin Profiler

=== Apple Developer Tools ===

Xcode 10.1 (14460.46)
Build 10B61

=== Xamarin.Mac ===

Version: 5.2.1.11 (Visual Studio Enterprise)
Hash: 5ef73d34
Branch:
Build date: 2018-11-21 00:03:25-0500

=== Xamarin.iOS ===

Version: 12.2.1.11 (Visual Studio Enterprise)
Hash: 5ef73d34
Branch: d15-9
Build date: 2018-11-21 00:03:24-0500

=== Xamarin.Android ===

Version: 9.1.0.38 (Visual Studio Enterprise)
Android SDK: /Users/fak/Library/Developer/Xamarin/android-sdk-macosx
Supported Android versions:
7.0 (API level 24)
7.1 (API level 25)
8.1 (API level 27)

SDK Tools Version: 26.1.1
SDK Platform Tools Version: 26.0.2
SDK Build Tools Version: 26.0.3

Java SDK: /Users/fak/Library/Developer/Xamarin/jdk/microsoft_dist_openjdk_1.8.0.9
openjdk version "1.8.0-9"
OpenJDK Runtime Environment (build 1.8.0-9-microsoft-b00)
OpenJDK 64-Bit Server VM (build 25.71-b00, mixed mode)

Android Designer EPL code available here:
https://github.com/xamarin/AndroidDesigner.EPL

=== Android Device Manager ===

Version: 7.7.1.0
Hash: 06ceaea1

=== Xamarin Inspector ===

Version: 1.4.3
Hash: db27525
Branch: 1.4-release
Build date: Mon, 09 Jul 2018 21:20:18 GMT
Client compatibility: 1

=== Build Information ===

Release ID: 707001868
Git revision: 8bcdfa96d67c8c88dc45728cc968a2f84b55322f
Build date: 2018-11-22 12:19:29+00
Build branch: release-7.7
Xamarin extensions: d66dbedcda237cd9b546abfecfeecafba6f8e3cb

=== Operating System ===

Mac OS X 10.14.1
Darwin 18.2.0 Darwin Kernel Version 18.2.0
Fri Oct 5 19:41:49 PDT 2018
root:xnu-4903.221.2~2/RELEASE_X86_64 x86_64

=== Enabled user installed extensions ===

MSBuild Editor 2.1.0
```