Fix server only, and broken test.

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MinecraftLibraryProvider.java

@@ -65,7 +65,7 @@ public class MinecraftLibraryProvider {
 					// Client only library, or legacy version
 					project.getDependencies().add(Constants.Configurations.MINECRAFT_DEPENDENCIES, library.name());
 				} else {
-					throw new RuntimeException("Library %s was not added to a configuration".formatted(library.name()));
+					project.getLogger().debug("Minecraft library ({}) was not added to any configuration", library.name());
 				}
 			}
 

src/test/resources/projects/simple/src/main/java/net/fabricmc/example/ExampleMod.java

@@ -9,6 +9,6 @@ public class ExampleMod implements ModInitializer {
 
 	@Override
 	public void onInitialize() {
-		LOGGER.info("Hello Fabric world!");
+		LOGGER.info("Hello simple Fabric mod!");
 	}
 }