EndToEnd.Tests.GivenDotNetLinuxInstallers is not behaving as intended

I question if the GivenDotNetLinuxInstallers EndToEnd tests are actually testing anything in CI runs. There is only one test in this test class which no-ops if the SDK_INSTALLER_FILE env var is not set. I am not finding anything that sets this. This test was migrated from the installer repo and hasn't been touched in 8 years. When originally written, the [build was setting this env var](https://github.com/dotnet/installer/commit/2d008aa4f74dabb7ab8b9e85aaa17d93dc1fc78f) when the linux installers were produced. This is no longer the case hence the test no-ops.