Build exception for certain string resources.

[yowl]

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• Bug report (I searched for similar issues and did not find one)

Current behavior

XamlGeneration fails for ResourceDictionary which contains
<System:String x:Key="shortDateFormatString">{0:d}</System:String>
Exception is

1>C:\Users\x\.nuget\packages\uno.sourcegenerationtasks\1.28.0\build\net45\Uno.SourceGenerationTasks.targets(100,4): error : Generation failed for Uno.UI.SourceGenerators.XamlGenerator.XamlCodeGenerator. System.AggregateException: One or more errors occurred. ---> System.FormatException: Index (zero based) must be greater than or equal to zero and less than the size of the argument list.
1>C:\Users\x\.nuget\packages\uno.sourcegenerationtasks\1.28.0\build\net45\Uno.SourceGenerationTasks.targets(100,4): error :    at System.Text.StringBuilder.AppendFormatHelper(IFormatProvider provider, String format, ParamsArray args)
1>C:\Users\x\.nuget\packages\uno.sourcegenerationtasks\1.28.0\build\net45\Uno.SourceGenerationTasks.targets(100,4): error :    at System.Text.StringBuilder.AppendFormat(IFormatProvider provider, String format, Object[] args)
1>C:\Users\x\.nuget\packages\uno.sourcegenerationtasks\1.28.0\build\net45\Uno.SourceGenerationTasks.targets(100,4): error :    at Uno.Extensions.IndentedStringBuilder.AppendFormat(IFormatProvider formatProvider, String pattern, Object[] replacements)
1>C:\Users\x\.nuget\packages\uno.sourcegenerationtasks\1.28.0\build\net45\Uno.SourceGenerationTasks.targets(100,4): error :    at Uno.Extensions.IndentedStringBuilderExtensions.AppendFormatInvariant(IIndentedStringBuilder builder, String pattern, Object[] replacements)
1>C:\Users\x\.nuget\packages\uno.sourcegenerationtasks\1.28.0\build\net45\Uno.SourceGenerationTasks.targets(100,4): error :    at Uno.UI.SourceGenerators.XamlGenerator.XamlFileGenerator.BuildChild(IIndentedStringBuilder writer, XamlMemberDefinition owner, XamlObjectDefinition xamlObjectDefinition) in D:\a\1\s\src\SourceGenerators\Uno.UI.SourceGenerators\XamlGenerator\XamlFileGenerator.cs:line 3670
1>C:\Users\x\.nuget\packages\uno.sourcegenerationtasks\1.28.0\build\net45\Uno.SourceGenerationTasks.targets(100,4): error :    at Uno.UI.SourceGenerators.XamlGenerator.XamlFileGenerator.BuildKeyedStaticResources(IIndentedStringBuilder writer, Boolean isGlobalResources, IEnumerable`1 keyedResources) in D:\a\1\s\src\SourceGenerators\Uno.UI.SourceGenerators\XamlGenerator\XamlFileGenerator.cs:line 886
1>C:\Users\x\.nuget\packages\uno.sourcegenerationtasks\1.28.0\build\net45\Uno.SourceGenerationTasks.targets(100,4): error :    at Uno.UI.SourceGenerators.XamlGenerator.XamlFileGenerator.BuildResourceDictionary(IIndentedStringBuilder writer, XamlObjectDefinition topLevelControl) in D:\a\1\s\src\SourceGenerators\Uno.UI.SourceGenerators\XamlGenerator\XamlFileGenerator.cs:line 596
1>C:\Users\x\.nuget\packages\uno.sourcegenerationtasks\1.28.0\build\net45\Uno.SourceGenerationTasks.targets(100,4): error :    at Uno.UI.SourceGenerators.XamlGenerator.XamlFileGenerator.InnerGenerateFile() in D:\a\1\s\src\SourceGenerators\Uno.UI.SourceGenerators\XamlGenerator\XamlFileGenerator.cs:line 232
1>C:\Users\x\.nuget\packages\uno.sourcegenerationtasks\1.28.0\build\net45\Uno.SourceGenerationTasks.targets(100,4): error :    at Uno.UI.SourceGenerators.XamlGenerator.XamlFileGenerator.GenerateFile() in D:\a\1\s\src\SourceGenerators\Uno.UI.SourceGenerators\XamlGenerator\XamlFileGenerator.cs:line 181
1>C:\Users\x\.nuget\packages\uno.sourcegenerationtasks\1.28.0\build\net45\Uno.SourceGenerationTasks.targets(100,4): error :    at Uno.UI.SourceGenerators.XamlGenerator.XamlCodeGeneration.<>c__DisplayClass20_0.<Generate>b__0(XamlFileDefinition file) in D:\a\1\s\src\SourceGenerators\Uno.UI.SourceGenerators\XamlGenerator\XamlCodeGeneration.cs:line 149

Expected behavior

This type of resource should be allowed to enhance compatibility with UWP

Minimal reproduction of the problem with instructions

Download the repo at https://github.com/yowl/UnoStandardRefTest/tree/FormatException and attempt to build the UnoLib project

Environment

Nuget Package: Uno.UI

Package Version(s): 1.42.0

Affected platform(s):
- [ ] iOS
- [ ] Android
- [ ] WebAssembly
- [x ] Windows
- [ ] Build tasks

Visual Studio
- [x ] 2017 (version: 15.9.4)
- [ ] 2017 Preview (version: )
- [ ] for Mac (version: )

Relevant plugins
- [ ] Resharper (version: )