[.NET 10] change default value for `PublishTrimmed`

[jonathanpeppers]

Android framework version

net9.0-android

Affected platform version

any

Description

Context: #9525
Context: dotnet/runtime#109724

As seen in the above issue, there is currently the expectation in .NET:

• PublishTrimmed=true set for all configurations, it means "I intend to trim this project"
• Not all builds need to actually run illink. For console apps, dotnet build doesn't trim or illink, dotnet publish does trim and run illink.
• .NET SDK sets various feature switches based on PublishTrimmed

Unfortunately, Android doesn't follow this pattern:

• Debug mode, PublishTrimmed=false for build performance, inner loop
• Release mode, PublishTrimmed=true

To fix this in .NET 10, we should:

• Set PublishTrimmed=true always
• Disable illink in Debug mode via other means

Steps to Reproduce

1. dotnet new android
2. dotnet build (debug mode)
3. Observe RuntimeInstanceNotAllowed Error Initializing XmlSerializer on Android Release Build in .NET 9 runtime#109724

Did you find any workaround?

For the case above you could set $(_DefaultValueAttributeSupport) as done in #9525.