[RISC-V] Fix HostActivation.Tests unknown-rid (#110687)

Author: sirntar

src/installer/tests/TestUtils/NetCoreAppBuilder.cs

@@ -356,8 +356,10 @@ public NetCoreAppBuilder WithStandardRuntimeFallbacks()
                 .WithRuntimeFallbacks("win-x86", "win", "any")
                 .WithRuntimeFallbacks("win", "any")
                 .WithRuntimeFallbacks("linux-arm64", "linux", "any")
+                .WithRuntimeFallbacks("linux-riscv64", "linux", "any")
                 .WithRuntimeFallbacks("linux-x64", "linux", "any")
                 .WithRuntimeFallbacks("linux-musl-arm64", "linux-musl", "linux", "any")
+                .WithRuntimeFallbacks("linux-musl-riscv64", "linux-musl", "linux", "any")
                 .WithRuntimeFallbacks("linux-musl-x64", "linux-musl", "linux", "any")
                 .WithRuntimeFallbacks("linux", "any")
                 .WithRuntimeFallbacks("osx.10.12-x64", "osx-x64", "osx", "any")